I actually understand where you are coming from where the rounds are too long, but definitely not in the 30's. I usually get bored with 4 player sometime after 40, but if I'm going for a high round that I haven't already done a bunch of times it is enough to keep me interested.
Part of the problem people are experiencing with Buried has to do with the WW and traps being used in conjunction with camping. Using a strategy like this on co-op, while extremely efficient at moving through the rounds, is dumbed down easy and BORING as hell.
Like someone up above said, after 30's is when the game really gets exciting because the zombies don't go down as easy, and if your teammates are dying off, it makes for a very hectic, exciting, fun, and adrenaline filled game.
I can understand why some people enjoy the set up of the early rounds(this is why I love the first hour of MotD and then bang my head against the wall the rest of the time), being without perks, guns and being forced to move through various parts of the map accomplishing different things.However, when it really comes down to skill and what separates good players from great players, it is the ability to train, revive, survive, maneuver and really CONTROL the game at a higher round.