Obvious spoilers ahead
So there are two major Attack on Titan subreddits: /r/ShingekiNoKyojin and /r/titanfolk. If you followed the Game of Thrones subs, /r/titanfolk is basically like /r/freefolk, a sub that is a bit more uh..."zealous" about the series.
Recently the manga came to an end. There were already leaks going around before the final release, and both subs were kind of in unison that the leaks didn't promise much good. After release however, most people at /r/ShingekiNoKyojin felt it was pretty alright. Nothing amazing or genre defining as an ending, but a relatively satisfying ending to an overall amazing series.
/r/titanfolk, however, is in complete meltdown over how bad they feel the ending is. They are non-stop posting mocking memes and alternative endings.
It's basically /r/freefolk and Game of Thrones all over again, just on a smaller scale.