By the time I saw Donnie Darko there were a lot of people who were convinced Richard Kelly was a genius. I watched it and I was like... aright, whatever.
His first movie was a 48-minute not-quite-feature that was hated by everyone. his third movie was a big budget catastrophe that was hated by everyone. His second movie is a piece of cult and okay, fine, but the fact that it saddled us with that horrific jules holland version of Mad World makes whatever good it has wholly drowned out by every mopey fucking pseudogoth manic pixie dream girl I've ever overheard in a coffee shop.
On a more serious note, the basic problem with time travel movies is it's the easiest fucking thing to turn the moral of the story into "it doesn't fucking matter." Best "it doesn't fucking matter" time travel movie? Twelve Monkeys. Worst "it doesn't fucking matter" time travel movie? Donnie Darko.
PROTIP: a film student trick, when your movie sucks and makes no sense, is to edit it into a nonlinear "thought piece." By making sure the end doesn't come after the beginning stupid people will think you're profound.