Marxisttypically what kills teams is this:
They become convinced that MGE/DM mod and how many 1v1s they win (since that's all that most combat classes experience objectively) is directly related to how good they are. As opposed to actually learning how to play the game.
So, those who fail just say "meh I'll DM more" or they quit because they don't have time to DM more. The others make it to IM, the ones that play the hardest will eventually make it to invite where they are inevitably crushed by the wave so to speak, because now it's all too apparent that they've never known how to do anything, so they just pack it in, quit the game, or change classes.
You have no idea how many people I've run into who've had 2+ seasons of experience in ESEA who had less understanding of how to play the game, and why certain things are done, than somebody who cursorily watched LAN once.
to be fair, I find it difficult to watch a full game, let alone an entire lan.