Seems fairly consistent with Star Wars prior to the sale to Disney. For example the mystery of the clones isn't actually revealed in the films. Sifo-Dyas is revealed to have created the Clones, but that's not even explained.

Not until 9 years after Revenge of the Sith when season 6 of Clone Wars comes out and finally explains that Dooku is Tyrannus (the Jedi never learned this on screen otherwise) and was directly behind the creation of the Clones.

In the movie itself, the only real explanation was Poe's now-infamous line, "Somehow, Palpatine returned."

I don't agree with this comment. The movie was not attempting to use this line as an explanation. That's really silly, Poe was literally just announcing the return of Palpatine to the resistance.