I've never been particularly invested in _The Simpsons_. This movie didn't turn me around on that. I could stand watching it, Hell, this was actually the **second** time I've seen it, but I assure you, it was not for my own enjoyment I did so.
_Final rating:★★ - Definitely not for me, but I sort of get the appeal._

Forgive this forward, but I literally watched all 31 seasons because I was sick and have never understood what the fuss was about the Simpsons.
I really have to conclude that the appeal of the Simpsons was a simple lack of options when it first came out, and then it just grew in power by simply existing for so long.
For this movie:
Uninspired watch, probably won't watch again, and can't recommend, unless you're already a Simpsons fan.
It's really just a lot of the Simpsons being Simpsons, but that also means that the overall story writing is actually pretty good, even if the character writing is rather repetitive.
I did enjoy the introduction of Ploppers, Spider-Pig, but it doesn't really even out everything else.
The big adversity is an "under the dome" scenario, which is actually interesting enough to explore, but because it's the Simpsons, we know that nothing ultimately interesting is going to happen, and that everything is going to resolve like its TV counterpart. Now, that said, the TV show does drop unexpected, unexplainable shifts, like the death of characters. I don't think Fox was brave enough to put such a thing in the movie, which would have completely changed the gravity of the movie.
It's fine, it's well produced, it's just not very interesting, and I don't think I'd ever watch it again unless I was binging the Simpsons again, and wanted to watch it in order.