I've read and heard a lot of things condemning Looper as "a time travel movie for stupid people." So far, it seems to me that the crux of these arguments rely on discounting the narrative's stated physics for time travel (whenever you are existing is the present, so the "future-events" that have yet to happen are dynamic) isn't how time travel works.
I'm sorry to break it to you, but time travel doesn't work. There is no time travel. When you are watching a movie that features it, you simply have to accept their explanation of how it works. That's what narrative is about. It doesn't matter if you think it works differently. That's called arguing the premise and if you do that when you are experiencing some narrative then of course you won't like it.
Looper posits this: there is something special about the subjective present. People traveling back from the future have vague memories of the possibility-cloud that lead up to their time-travel jump but, since it hasn't objectively occurred yet it is in flux. As things solidify into the subjective present, new memories spring into place. You're free to dislike that on any grounds you want, but saying that it isn't how time travel would work is just juvenile and laughable.
That is all!