im not a big fan of crits, i hate it when i get killed in one shot because of a crit...
spawn camping i dont mind so much, if your team is bad enough to let a spy just hang around and backstab or have a heavy medic combo outside the door then you deserve to get picked up. just get a medic and hit em back. i play pyro pretty much always, and there are times when (especially on payload maps) where i can just mow people down, work my way back to spawn, i take out teleporters, kill a few people, but they get me eventually.