Pardon me, mister, but recently I just started fresh KF account with reset perks and two days ago I finished 7th wave alone with 160 zeds remaining when my party was wiped out, on suicidal difficulty as a lvl3 sharpshooter.
It has a LOT to do with skill, but yeah, I agree that someone who just got lvl4 and didn't play KF before is not usually ready for suicidal servers.
That's not because you "have skills" or such. That's because you already played the game thousands of times, which implies knowing the "spots", zed's pattern, which weapon is the best for which, which zed you have to AVOID AT ALL COSTS IF YOU HAVE ONLY A 9mm INSTEAD OF GOING KAMIKAZE ON IT.
You can be the best gamer in the world, but whenever you play a new game (especially the surviving ones like Killing Floor, Left 4 Dead, Zombie Panic!, Zombie Master), it takes a while before you can really get into it.
I'm not saying newbs aren't welcome. Whenever I see one, I try to help him enjoy the game, but it pisses me off when I'm playing suicidal, get to the 9th wave and then someone on lv 2 joins and starts shooting FPs with 9mm, or hitting them with the knife, making it rage and slaughter half of us, if not the entire team. More annoying when you tell them that the difficulty is too high for their level. The response? "I don't care" "orly?" "*Insert random cool 4chan statement*". Newbies are one thing, trolls are another.