Well, I think you are a bit clueless. There are a LOT of great new metal bands. For example... Eluveitie, or Swallow the Sun. That evolutional process is not the problem, the question is, if you think we have to accept that crappy childish bands like BFMV or Callejon on Wacken, just because music evolves (according to you) in that direction, maybe it's you who should remain at home in order to save us from your bad taste.
This is the 20'th anniversary, and you really can't do better? Heaven & Hell is great, Napalm Death is also great, and a few more bands too.
But it really seems most of the bands in Wacken are the remains from the other europe fests.