While I agree that these achievements in wotlk were toxic and stupid as they were not player choice but team effort and you had to have 24 competent people… it is still an incentive to for why people play x y z expansion.
So the argument of that it would lose subs is whatever as they retain subs because of such difficult and long tasks for people that are knowingly going away.
Cata has none of this. So you can play in peace or just something else. Nothing to miss out like in wrath.