Of course it's fair to doubt him. He's made two lousy films in a row,
the most recent of which is quickly earning some kind of legendary status. (You're seriously underselling just how much the Book of Henry has been derided.) His Star Wars movie might end up being great -- movies are bad for all sorts of reasons -- but at this early point there's very little reason to have positive expectations of any sort. If people were calling for a boycott
that might be unfair, but I don't think that's really the case here.
But I feel the one thing you can be confident about is that Episode 9 will have plenty of fans and be very successful regardless. (Look at all of the people who loved a mess like Rogue One.) In that sense Trevorrow is a safe pick, because as long as he can successfully shoot the damn thing it probably won't hurt Disney's profits.
(I won't lie, I giggled about the Twitter block.)