I don't know why people insist on crediting Solo's fate to TLJ. Solo was a (almost entierly) pointless story. It was the first Star Wars film I didn't go to see in the cinemas, and it had 0 to do with TLJ.
It's pretty simple really. When thousands of fans say that TLJ killed the franchise for them, of course that's going to affect future entries into the franchise. Even with all the crap surrounding Solo, it should have easily broken even. Instead it flopped. A franchise first.