After rewatching TLJ I don't dislike it as much as when I first saw it. It does have some epic moments as others have mentioned, but it also has some epically bad moments (Leia doing a Mary Poppins in space) I can now watch it and enjoy it for what it is and I still think it's better than the prequels.
What I find odd about JJ's comments is that he wrote the script draft for TLJ and still had producer credits. If he was unhappy with certain elements of the story he should have stepped in and changed them, particularly if he thought it would affect how ep 9 plays out.
JJ and Kathleen Kennedy supposedly had the story arc for 7, 8 and 9 mapped out before he started filming TFA.
He must have been happy with it at the time and he's doing damage control now and trying to lessen his liability if Episode IX is a flop.