If you're making a time travel movie, you must establish the rules in which the story is going to take place. That's basic stuff.
For me, the problem with Looper is that there's wasn't any explanation of how time travel works in that movie. In fact, when they are about to start talking about it, Bruce Willis' character just shuts down any possibility.
I mean, the most interesting thing about time travel is how it works and how is going to affect the story. Looper made a huge mistake on that, and so it lost me completely as a viewer. Is like 'anything can happen' with the telekinesis and the time paradoxes -that they didn't even try to explain-.
Though an interesting concept, I think Looper is an overrated mess.