I'm a progressive, but also a pragmatist and a realist, and I find these kind of complaints unhelpful and naive. Politics is a blood sport and it always has been. No one is going to hand AOC the reins of power. She has to win them, and her opponents aren't going to play fair. This is, sadly, how the game is played. Don't mourn. Organize!
Just a few weeks ago there were left voices mad that the party wasn't preventing Andrew Cuomo's campaign to be mayor of NYC. I didn't see any one on the left crying foul over suggesting the party shouldn't play fair.