Your comment sounds asinine, since you consider alternative metal only as a genre involved with "MALL"core and genres like nu metal and rapcore that probably you consider as shit and since you say "Katatonia is still metal" (maybe because you don't consider these genres as metal genres?). However, alt metal is not equal to nu metal or similar (but it is a subgenre, and TGCD is also lightly influenced by nu). And finally... "dark metal" doesn't exist, "dark" is an attribute that could be referred to a lot of different stuff, goth rock, death rock, gothic metal, doom... sometimes even death or black, or many industrial bands that sound "dark". Yes, an album could sound "dark". But like it could sound "harsh", or "happy", or "gloomy", or "melanchonic" etc. and "dark metal" doesn't exist. 
 Sorry for my English.