ROS had plenty of places to go with the plot hooks left by TLJ. The struggle of Kylo Ren in the classic will he/won't he stay evil arc, that is pretty much standard issue Star Wars plot devices for villains. Whether or not Rey is capable of stopping the rising influence of the Dark Side in Kylo, and whether or not she can/should redeem him, again, a VERY common SW trope. Whether or not the Resistance can survive the increasing growth in power and scope of the First Order. Whether or not the Jedi (or some variant of them) will survive to try and continue to serve as protectors of the galaxy against the influence of the Dark Side. Will Poe rise to the occasion and be the leader of the Resistance that is needed to win the day. Will Finn find a place for himself in the galaxy, after he forcibly rejected his conditioning as a child soldier, and make a life where he can find satisfaction and peace. Will X ship with Y for multiple pairings.The Last Jedi really didn't leave anywhere for ROS to go. Yes, there were some big world changing consequences that could be explored, but they should have been saved for the final movie, to set up the next trilogy or a new TV series. They couldn't be wrapped up in a single movie in a satisfying way.
Rian Johnson prematurely ended the story arc.
Tons of things, most of which ROS ran with anyway.
As for my personal thoughts on the films, I enjoyed FA just fine, and really enjoyed TLJ. It didn't like blow me away, but it was fun. And they did a few visual storytelling details in certain scenes that I genuinely think were brilliant. I like the general thrust of the narrative. It's got some clunky bits, like I don't really care for the Canto Bite portion, but I don't have a problem with it being there, as it serves as much narrative purpose in the film as the Falcon B plot in Empire strikes back. Namely that it's a side plot to the more emotionally weighty and mystical Force narrative/training sequence, follows the rest of the supporting cast, is mostly for comic relief and tension breaking, and ultimately doesn't actually accomplish the goal set out by the group initially.
Rise of Skywalker just annoyed me, on so many levels. I don't hate it, as frankly I just can't bring myself to be that invested in any of this pop culture stuff anymore. I didn't think it was a very good film. It had a few good parts, but was mostly frustrating and disjointed for me. But it's not the end of the world, it's just a movie.
The Solo film, I really enjoyed, like a lot. I found it very enjoyable in almost every way, and aside from the times it tried to forcibly remind us "HEY! THIS IS PART OF STAR WARS!! SEE! THIS CHARACTER IS MAKING A CAMEO!" I have no issues with it.