Lucas is understandably salty as fukk but I can also understand it. The situation must be sad and confusing for him. He's sort of a father figure to a whole generation of people that grew up on the originals and loved him, and he watched his ideas gain a life of their own and become a part of the world's pop culture. But now he's at a point where those ideas are the world's, but no longer his. he probably felt comfortable selling LucasFilm also thinking that his ideas would be received and that he would still be able to participate in his own creation and his own universe/sandbox. Once they told him to
I'm sure it hurts really bad. Especially to see how successful and critically praised this new movie is after his last 3 contributions were almost universally shyt on. I'm sure he's jealous and angry. At the same time, despite how much the prequels are basically unwatchable (IMHO), I do believe he thought he was trying some original ideas, however lazy or lame-brained they were. So he's seeing that they basically re-did A New Hope and it's an easy point where he can call them lazy or creative.
But he's still wrong. I mean yes, A Force Awakens did have a lot of callbacks and familiar beats, arguably too many, but most of us agree it sets the stage well for a new cinematic universe of Star Wars films, and that the franchise is in much better hands without his ideas.
You go back and hear stories of how Lucas had so many people to check him on the old films that weren't yes men, and stories of how he wanted Han Solo to be a dirty orphan, or Boba Fett would be Luke and Leia's uncle, making Fett and Vader brothers. Or even in the prequels that Darth Maul was going to look like this
Goofy shyt like that, and then you see his awful prequels where he had all yes men, and you start to wonder just how much better the originals were because other people besides Lucas were involved.