I think its not the originality
its the progression

Diablo II isn't original
when I played Barbarian I just buff myself, pick concentration and do nothing but holding right click
it was fun because game keeps progressing eventaully... not like that sh*tty Battle of Immortals, game really progresses

everygame is the same
even RuneScape
in other MMORPGs you level up by killing mobs over and over again
in RuneScape you level up smithing by smithing over and over again

there is no progression