It wouldn't be so stupid with more polished dialogue. The Son is powerful, but emotionally unstable; the Sith manipulating him isn't that far out in left field, and could be symbolic of the Sith's ideology of imposing their will on the Force.
I actually do have more of a problem with canon Sith transcending the mortal plane, myself. I feel like the closest thing to immortality the Sith should be able to achieve is something like what we saw in DE.
Maybe it would have worked if they were something like those time-transcending visions the Son showed Anakin.
I don't want Sidious returning, period. And certainly not when we have Snoke now. I mean, how much can you undermine a villain's intelligence or their holistic portrayal? Not that I believe it, but if Snoke is Plagueis, then that already undermines Palpatine's character as a whole. If Palpatine returns, then Snoke gets undermined as well.
They should just leave it alone. It also gives Vader's sacrifice more depth.
I mean, I enjoyed some aspects of DE, but I don't think it has any chance of happening again in this day and age, and that's for the better. Also, they ruined Palpatine's character in it, lmao.