It's a real shame because the season 2 finale set up so much red meat for this season that this show finally had the opportunity to stand on its own two legs as opposed to simply being "the series after TCW."
Here is what season 3 should been about:
#1. Ezra's slow and gradual descent towards the dark side.
Not the mustache twirling dark side disney interpretation of the dark side, but where the choices and decisions actually make sense, are logical and morally ambiguous and perhaps even give viewers stuff to think about. Needless to say, the season 2 finale and the buildup beforehand should have had some serious effects on his psyche. Ezra becomes absolutely OBSESSED with defeating the Sith throughout the entire season.
#2. Kanan does NOT immediately get accustomed to his blindness.
This should have been a gradual process throughout the entire season as opposed to being resolved in like two episodes. I like that him being blinded by Maul puts some distance between him and Ezra, but this should not have been something gets resolved the minute its explained. By limiting Kanan throughout nearly the entire season, it makes the part where he finally recovers (i.e. a crucial moment in the Season 3 finale) that much more satisfying and gives Ezra more justification for working and learning on his own.
#3. Maul is actually relevant/
Knowing what we know now, Maul served very little purpose throughout this season. The writers were trying to give us this idea that Maul and Ezra were going to work together inadvertently/advertently to achieve some goal. What we got was some lamebrain kidnapping scheme by Maul in one episode, an ultimately pointless encounter with the Night Sisters and a 2 minute cameo from Obiwan. You could take the Maul episodes out of season 3 and nothing would change. Much like the 'darkside Ezra subplot', Maul had zero impact on the narrative throughout this season, so why bother? He may as well have been killed off by Kanan in season 2. Wouldn't have mattered.
Instead, here is how I believe Maul should've been used: From his point of view, he'd be secretly training Ezra in the hopes that they could both use the secrets of the Holocron together to destroy Palpatine. The words "Obiwan Kenobi" should have never been mustered throughout this entire season. From Ezra's point of view, he'd have accepted Maul's tutelage (in secret) as a necessary evil to become powerful enough to destroy the Sith. Remember, the events of the previous season have pushed Ezra to the point of obsession, so he's even willing to work with the guy who blinded his master and father figure if it will get him results.
Slowly but surely, we'd start to see Maul develop as a character. Learning from his mistakes in the season 2 finale, he'd be subtle in his approach of keeping Ezra as his apprentice (never even calling him his apprentice even though he considers him that). Over time, we'd start to see Ezra and Maul's dynamic have opposite effects on one another (Ezra shifting further towards the dark side and Maul slowly shifting in the gray direction without realizing it). Maul won't admit it, but is slowly becoming fond of Ezra's companionship.
All the while, the Ghost Crew would become increasingly suspicious of Ezra and what kind of activities he was frequently engaging in on his own. Obviously, Kanan and co would confront Ezra on this in the end upon realizing it, but this would be a great source of tension and drama throughout the season as well as the keep viewers guessing on what's going to happen next.
#4. Thrawn flips the show on its head
The way they had been building up Thrawn throughout the season was good, but there was very little payoff in the end. We don't care about the Rebels losing a sizable percentage of their forces; we've all seen A New Hope before so we know that doesn't matter. Despite the name, this show isn't about the Rebels. This show is about the GHOST CREW. This show is about Ezra, Kanan, Hera, Sabine, Wrex and Chopper. So what we really needed to see in this finale was Thrawn delivering a deadly blow to the Ghost crew on a personal and emotional level. And given the significance the Rebels have had as a result of the Ghost Crew's antics, it would've made sense for Thrawn to have some awesome unbeatable plan that accomplishes just this even if he isn't able to destroy the Rebel Alliance. Thrawn needed to do something so CRUSHING and DEMORALIZING that was just going to flip the status quo on its head and make Season 4 a whole new experience. Killing off a member of the main cast, instigating a betrayal, etc.
#5. No pointless filler
This means gutting a lot of season 3 in its current form.
#6. No walking plot device coupon giving Bendu ex machina.
Speaks for itself really. Lazy writing. Extremely lazy writing throughout this season. Bendu should have never existed.