What made the first trilogy legendary?
Simple. Good vs evil
Simple. Character Development
There were things Luke would and wouldnt do. Same with Han and Leia.
When you complicate things; you ruin them. Vader was evil. The empire was evil. Luke was Good.
Not so tough
The original Star Wars was fun. It was a space swashbuckler and did not take itself so seriously.
The Empire Strikes Back wasn't as fun because they started getting more serious.
Return of the Jedi jumped the shark by including Teddy Bears.
To Disney: $$$$$$
To fans: Characters they liked doing really cool things, even the bad guys.
There was some question then and now whether the Dark Side or the other side of the Force would prevail in both heroes and villains. You had to have some of that conflict for the movies to be interesting.
I'm not so sure that things got complicated and were ruined by it. Rey, the new girl, is a very simplistic character, and so is the evil old White guys versus good young multiracial multi-gender guys schema.
I agree that complicating things, especially on the good and evil front, ruins a whole lot of things (forget Star Wars, we already learned that lesson with the 2014 Maleficent film.). Unfortunately, I’m currently hesitant to call Luke Skywalker good, or the Empire and Vader evil, largely thanks to the fact that George Lucas actually DID based the Empire on America, and the Rebels on the Vietcong, meaning he STILL tried to do a subversion of traditional good vs. evil by depicting the Vietcong as the good guys despite objectively having much more claim to human rights violations than the Americans did.