Back in the day, every class was made with an RPG mindset, aka each had its own strengths and weaknesses (Vanilla/BC). WotLK drastically changed that, with the famous "bring the player, not the class" mantra - so dps/healing/tanking was normalised so that everyone could do everything (except at VERY high play level).
Therefore, if you are going to have the same e.g. DPS than any other class, you should also have the same utility, or close - aka MoP design. Otherwise you end with things like the BfA rogue, which is simply OP (in PvE) because not only has the same DPS than any other melee, but also a truckload of utility on top.