actually first “wow” version of diablo was D3.
Cooldowns, gen system, rotations, scaling and etc - those were Wow mechanics and was implemented in D3. That was and is not an ARPG mechanics.
Now in D4 they just implemented more MMO mechanics such as coop-dungeons(you can call it raid, whatever), weekly rewards, “open” world and etc.
In my opinion, the reasons are purely commercial cuz it’s way easier to get money via your mtx shop for mmo, than for ARPG.
Is it bad - yes, but wcyd ?