An MMORPG has its roots in Dungeons and Dragons and then other games that came forth from that. These games focus mainly on the long term decisions that players employ such as which gear to use, which stats to distribute, which spells to cast, and which choices to make in the story.
A player’s efficacy in combat relied on the rolls performed, not on reaction speed, dexterity (IRL), and honed attention. The fast paced combat that we see now is comprised of attributes of different genres which have slowly made their way into the MMORPG space mainly from WoW post-wotlk. Even classic WoW was more similar to its predecessors in that the combat was fairly straightforward and wasn’t trying to make you cast an ability every global cooldown.
The history of MMORPGs, which have it’s spark originally from Dungeons and Dragons progressed into Runescape, Everquest, Ultima Online all of which had similar combat experience, that of slow paced decision making. MUDs have an auto turn based combat as well. The simplicity of combat wasn’t boring, it allowed for a more immersive roleplaying experience rather than feeling like Galaga. What made your character in D&D and Everquest was not quick skill (with some exceptions in Everquest being mezzing multiple mobs on big pull, charming as enchanter, etc). This brings me to another point of why combat in WoW is flawed:
In WoW every pull is a diablo style AOE fest. This is another more recent development in the MMO space that took place mostly post wotlk. Enemies are no longer intimidating and they don’t command respect because they are inconsequential and numerous. This also hurts immersion as players don’t appreciate each of the enemies and instead probably can’t name trash mobs from 5 man dungeons. If there were few and focused enemies, people would pay more attention to the details. This is also a common argument against flying. When you traverse the environment quickly, there is less time to actually see it. This reduces the appreciation of the artistic design choices employed in the environment that the developers worked so hard to create. All the details are destroyed as the game becomes more and more fast paced, whether it be quickly traversing through the air or bulldozing trash packs in a dungeon.
The fast paced combat in WoW is more important to highly competitive games such as FPSs and MOBAs where physical skill (dexterity), mental alacrity, and quick problem solving and strategic planning (MOBAs) come into play.
Of course there is no absolute definition of what an MMORPG is, and even if there were, doesn’t mean it shouldn’t be strayed from, but if we look from a historical lens at what the genre is and what it means, we see that as it drifts closer to fast paced competitive gameplay style, it simultaneously drifts away from immersion and away from the roleplay aspects.