we know all we need to know about those characters - adding more diminishes them.
Do something new, expand the universe, actually write something good, now there's a novel thought.
I 100% agree with this.
What 7, 8 and 9 should have been was to introduce newer characters and help them mature whilst you slowly phase out the rest of the characters through that time so it's been passed over to the new kids (not even necessarily during this trilogy). That way, as the new cast is spread out to newer films and stories, there is investment in them. And if needed, you have the old cast to help push it a little longer until the new cast takes hold.
Now? Han is gone. Leia's actress has passed away (though she would likely have returned in 9). Luke is gone. And no one really cares what happens to the new kids yet. And all they had to do was a rewrite so Luke remained so they could finish passing "any" type of batton to the new kids in 8. But nooooo.... That totally would have been to expectations. But don't worry, so long as you create new characters, a new trilogy, or rewrite existing ones into a whole new light, the people will come anyway, because "Star Wars" right? Well, Solo proved that right didn't it?
Meh. They wrote themselves into a hard corner they can't come out of. Because of an actress' passing, something they still had minor control over at the time wasn't done to undo the corner they got stuck in wasn't done, because 8 wasn't released yet. But anyway, enough of my ranting over that. What's done is done. And Star Wars forevermore as far as I'm concerned is 1 to 7. I can't see 9 being any good unless they are prepared to forgo "professional courtesy" and give 8 (and so Rian Johnson) the middle finger and make it a "Force Premonition" sequence or something. Which they won't do. So again, for me: Star Wars = Phantom Menace, Attack of the Clones, Revenge of the Sith, A New Hope, Empire Strikes Back, Return of the Jedi, and finally Force Awakens.
And to think that it all could have been so much more...