Solo came pretty soon after TLJ so maybe some franchise fatique/backlash to TLJ hurt it a bit.
Curiously, it's kind of the most traditional SW film in a few ways. Written by an original trilogy writer, and a man who was a colleague of Lucas (Ron Howard, although he did pick it up after the original directors left). if the prequel trilogy had come out earlier or even sequels it's likely Howard would've probably directed at least one had Lucas decided to not do the whole thing himself/
As for the cancelled films, I think Josh Trank's film was dropped mainly because of how much of a disaster his FF reboot was and also his behavior.
Colin Tremorrow released from Episode 9 was a bit trickier, perhaps because he largely followed many of the story directions TLJ took things in with his script instead of Abram's reset button approach. The death of Carrie Fisher the year (His draft was written before her death) before probably didn't help as the film required a bit more of Leia. There's also his non-Jurassic World films not doing so great.
Read Jenkins is kind of difficult to work with and has issues getting projects off the ground and WW1984 probably didn't help.