Messing myself into this discussion, here is what I think:
First off, TLJ didn't "suck". It had a lot of flaws, and I won't pretend they aren't. But the quality of the film was way above it's big flaws, so I can forgive that. I actually left the theatre with a false sense that it was the best Star Wars movie ever, but of course that didn't last. I loved the movie when I first watched it. I was disappointed by some parts of the movie, but for the most part, I loved it. I will say that the movie definitely deserves the 91% score given by the critics on Rotten Tomatoes. I feel like the only reason people hated this movie was because... well... expectations. A movie should be considered good or bad by the level of entertainment it gives you. For me, it absolutely entertained me. Most die-hard Star Wars fans went to see the movie for the sake of the Franchise rather then to be entertained by the movie.
So in the end: Did this movie suck? No. It made a tone of money at the Box-office, and it got a great score from the critics. So, it's no way it can be considered a failure from a cinematical point of view. From the fan's perspective however, which spent all their time since TFA came out theorizing who Snoke is, Who Ray is, then yes, it was a failure. Star Wars is a great franchise, but fans should not waste their time theorizing when all the movie's fate in in a director's hands. J.J Abrams has the power to do whatever he wants with Star Wars, and fans can't change that. So you have two options:
1. Enjoy the film because it's good.
2. Waste your time trying to predict what will happen in the next movie when your predictions will turn out completely wrong.
As far as the problem with Solo, the reason it didn't do well at the box-office is because it's a Spin-off. People would go see the main Saga, not a Spin-off. And most fans didn't really wanted a movie about Han Solo, so giving them something that they didn't really care for just because it's "Star Wars" did not help. And the movie wasn't a box-office hit, but at least it did more then it's budget, so It can't be considered a failure either. And the 70% score given on Rotten Tomatoes isn't bad either.
I am not the biggest SW fan out there, but I hope this post helped.