I thought it was like a decade too late but despite the film coming out at a point where I was the most far removed from current Simpsons I had ever been and not necessarily being interested in a film that I was pretty skeptical of being good, I was there in the theater.
I enjoyed it, and while I felt it was good but not great, thought it paid tribute but could have went farther, thought it was underwhelming, too safe, played on too many Simpsons tropes for episodes we've seen before (Homer going on a spirit quest, the Simpsons moving out of Springfield, Homer getting a weird pet, Lisa finding a boy that likes her but her family ruins it for her, etc.), there are so many gags that feel more memorable that many current episodes and even some past ones during the more revered eras. In fact, I often laugh about some Simpsons movie gags completely forgetting that they aren't in any episode but in the movie.
In that way, I think it's had a similar path for me as something like the South Park movie, where my expectations for what could be possible are so high that I can't help but be disappointed when it just doesn't go in the direction that I hope, but looking back, it's much better when viewed on it's own merits than I might have realized, even having enjoyed both films. In that sense, I think I might have thought I enjoyed the Simpsons movie but didn't feel like it was a film that needed to be made at the time, but now I feel like it absolutely needed to be made, since it deserved a good film, even if it passed the point where the best possible Simpsons movie might have theoretically been made. It also struck a good balance of paying tribute to the series but not going overboard of relying on nostalgia and references.
the only part that I felt was weak was Spider-pig. Of all the Simpsons gags that had been done before in this film, I thought most of them were good if not great and well-worthy of being put amongst some of the great Simpson gags, but I didn't feel they did enough with Spider-pig to rank with my favorite Simpsons pets like Stampy, Pinchy, Mojo, Duncan, and Santa's Little Helper. Also the villain was pretty forgettable. Hank Scorpio would have been great.