Azronger
This essay isn't about the new films (I've already given my thoughts on them here), but rather the sequel trilogy as a concept. This is about why to having more movies taking place after Episode VI is fundamentally a flawed idea, and can only work well if very specific, nearly-impossible-to-attain criteria are met.
First, let's establish that the Star Wars films at their core are the story of Anakin Skywalker. Episode I shows him as a small kid, explains his origins, and has him set off on a grand adventure to become a Jedi Knight with the intended purpose of bringing balance to the Force since he's the Chosen One and all that. Episode II shows him on his quest, learning the Jedi ways, and sets up the threat of the Clone Wars and the hardships Anakin will have to endure to prevail. Episodes III and IV serve as the second act in the classic three-act structure where the heroes lose and are at their lowest point; for Anakin, this is when his hamartia results in him losing his loved ones, his humanity and his soul to the devil who in this case is represented through Darth Sidious, and he's reduced to a tool for the Empire whose only purpose in life is now is to please and run errands for his Master. Episode V is where things start to work in Anakin's favor again, and he sees an opportunity to set things right and get out of his misery through his son, Luke, and starts working towards that goal. Episode VI is where all the plotlines culminate, and Anakin redeems himself by fulfilling his intended purpose in bringing balance to the Force and destroying the Sith, meaning the Emperor but also himself, and he regains the things that he lost, mainly his humanity, but also his loved ones as seen at the end.
Thus, the purpose of Anakin's death at the end of Episode VI serves three narrative functions. First, it is the fulfilment of his existential purpose, the reason for why he's in this story in the first place: to bring balance to the Force, and he does this by killing the Sith, which he is a part of, so his death is in a way part of the prophecy. Second, it is the fulfilment of his personal goal: Anakin isn't just a plot device, he is a person, so he has some personal stake in the story as well, and that is to love and to be loved eternally, motives that are mostly explored in Episodes II and III, where he exclaims his desire to learn to prevent himself and others from dying so that he can feel and express his love forever; by sacrificing himself for the sake of his son, he has regained his love for his family, and in death he can finally be with his loved ones eternally as is shown in the final scene with him as a ghost, which is what he wanted all along. And finally, the third narrative purpose Anakin's death serves is as a signal that the story has come to and end; it's his story, so you can't tell the story without him in it, so when he is gone, it means that there is no more story to tell.
And that's the fundamental reason why the sequel trilogy should not exist. Anakin's story has already been told. No, Anakin isn't the only person in the universe and the galaxy will continue to exist and evolve long after him, but that's what the Expanded Universe of books, comics, and other media is for. The films are meant for this particular story - Anakin's story - and for nothing else. You might say that the films are also Luke's story, since he's the protagonist for half of them, but that's a misconstrued view things. Even in the original trilogy, when viewed in the context of the larger saga, the story is still about Anakin. It is told through Luke's perspective, but it is not his story (like how much of the prequels is told from Obi-Wan's point of view, but the story still isn't about him); it's the conclusion of Anakin's story but only a small chunk in Luke's story; he still has a Jedi Order to rebuild and a New Republic to establish, but all that was told in the books because the films aren't about Luke. They're about Anakin: his birth, life, and death.
The only possible way to make a another trilogy after Episode VI that I can see is to have it be about Anakin's legacy, the immediate consequences of his life's decisions and what he left behind in the galaxy, but the proper execution of something like that would be so hard I honestly have no clue where you would even begin. The primary reason for that is that the new trilogy cannot tell its own story; it has to be part of Anakin's story. You'd essentially have to produce three films of material about a guy who isn't even alive anymore; come up with a narrative and thematic purpose for these films' existence, so that it feels like an organic part of the story, enrichens the previous films, and is important enough that the overall narrative would be lesser without it; and extend plot threads for three whole films when every single one of them has already been concluded, basically meaning that you'd have to somehow make Episode IX a more meaningful, satisfying and fulfilling ending for Anakin's story than Episode VI, the part where he dies and finishes both his existential quest for the prophecy and personal quest for love everlasting. If you somehow can pull all of that off (you can't), then I'm onboard with your sequel trilogy, but otherwise, no thanks.
Now, I'm perfectly aware that what I'm describing might not even be humanly possible, but that's the thing: you don't edit art after it has been finished. The sequels as a concept are essentially the equivalent of if someone started making unnecessary additions to the Mona Lisa or whatever work of art you can think of, with the end result being worse with a certainty of 99.99999999999999 %.
First, let's establish that the Star Wars films at their core are the story of Anakin Skywalker. Episode I shows him as a small kid, explains his origins, and has him set off on a grand adventure to become a Jedi Knight with the intended purpose of bringing balance to the Force since he's the Chosen One and all that. Episode II shows him on his quest, learning the Jedi ways, and sets up the threat of the Clone Wars and the hardships Anakin will have to endure to prevail. Episodes III and IV serve as the second act in the classic three-act structure where the heroes lose and are at their lowest point; for Anakin, this is when his hamartia results in him losing his loved ones, his humanity and his soul to the devil who in this case is represented through Darth Sidious, and he's reduced to a tool for the Empire whose only purpose in life is now is to please and run errands for his Master. Episode V is where things start to work in Anakin's favor again, and he sees an opportunity to set things right and get out of his misery through his son, Luke, and starts working towards that goal. Episode VI is where all the plotlines culminate, and Anakin redeems himself by fulfilling his intended purpose in bringing balance to the Force and destroying the Sith, meaning the Emperor but also himself, and he regains the things that he lost, mainly his humanity, but also his loved ones as seen at the end.
Thus, the purpose of Anakin's death at the end of Episode VI serves three narrative functions. First, it is the fulfilment of his existential purpose, the reason for why he's in this story in the first place: to bring balance to the Force, and he does this by killing the Sith, which he is a part of, so his death is in a way part of the prophecy. Second, it is the fulfilment of his personal goal: Anakin isn't just a plot device, he is a person, so he has some personal stake in the story as well, and that is to love and to be loved eternally, motives that are mostly explored in Episodes II and III, where he exclaims his desire to learn to prevent himself and others from dying so that he can feel and express his love forever; by sacrificing himself for the sake of his son, he has regained his love for his family, and in death he can finally be with his loved ones eternally as is shown in the final scene with him as a ghost, which is what he wanted all along. And finally, the third narrative purpose Anakin's death serves is as a signal that the story has come to and end; it's his story, so you can't tell the story without him in it, so when he is gone, it means that there is no more story to tell.
And that's the fundamental reason why the sequel trilogy should not exist. Anakin's story has already been told. No, Anakin isn't the only person in the universe and the galaxy will continue to exist and evolve long after him, but that's what the Expanded Universe of books, comics, and other media is for. The films are meant for this particular story - Anakin's story - and for nothing else. You might say that the films are also Luke's story, since he's the protagonist for half of them, but that's a misconstrued view things. Even in the original trilogy, when viewed in the context of the larger saga, the story is still about Anakin. It is told through Luke's perspective, but it is not his story (like how much of the prequels is told from Obi-Wan's point of view, but the story still isn't about him); it's the conclusion of Anakin's story but only a small chunk in Luke's story; he still has a Jedi Order to rebuild and a New Republic to establish, but all that was told in the books because the films aren't about Luke. They're about Anakin: his birth, life, and death.
The only possible way to make a another trilogy after Episode VI that I can see is to have it be about Anakin's legacy, the immediate consequences of his life's decisions and what he left behind in the galaxy, but the proper execution of something like that would be so hard I honestly have no clue where you would even begin. The primary reason for that is that the new trilogy cannot tell its own story; it has to be part of Anakin's story. You'd essentially have to produce three films of material about a guy who isn't even alive anymore; come up with a narrative and thematic purpose for these films' existence, so that it feels like an organic part of the story, enrichens the previous films, and is important enough that the overall narrative would be lesser without it; and extend plot threads for three whole films when every single one of them has already been concluded, basically meaning that you'd have to somehow make Episode IX a more meaningful, satisfying and fulfilling ending for Anakin's story than Episode VI, the part where he dies and finishes both his existential quest for the prophecy and personal quest for love everlasting. If you somehow can pull all of that off (you can't), then I'm onboard with your sequel trilogy, but otherwise, no thanks.
Now, I'm perfectly aware that what I'm describing might not even be humanly possible, but that's the thing: you don't edit art after it has been finished. The sequels as a concept are essentially the equivalent of if someone started making unnecessary additions to the Mona Lisa or whatever work of art you can think of, with the end result being worse with a certainty of 99.99999999999999 %.