He's absolutely not "done" in the NHL at age 24. Goaltending doesn't work like that.
He has 15 minutes in the NHL. Granted, they were 15 horrible minutes against the Blues, and it certainly would have helped if he looked as good as Mrazek did as a 20-year old. But the AHL track record has been pretty encouraging since then, and that was basically his team in GR last year.
I'm not saying Tom McCollum is an NHL goaltender. I'm saying that it's dumb to assume that he isn't based on one terrible performance where he didn't even play a full period, let alone a full game.
One of my favorite Twitter things ever, however, was the day it was reported that he was being released by the Wings, so all the bloggers opened the floodgates with every terrible Tom McCollum story they hadn't reported before, and then he was re-signed a few hours later. Haha.