Why does OSRS Slayer combat feel so different from most MMOs? Why do not other mmos implement this?

I always liked OSRS Slayer combat with how simple it is. You mostly let your character autoattack, make a few decisions here and there, and move on to the next NPC with things like slayer.

It feels very different from MMOs where combat requires constant ability use and attention.

What other MMO combat systems have that same kind of low-input, autoattack focused feel?