A multiplayer RPG usually involves classes, roles and specific mechanics to follow to beat an opponent. Just look at DnD specifically, one of THE RPG genres both with pen/paper and video games by now (see Baldur’s Gate 3). There is no “universal” RPG definition, since it is quite the broad genre.
A Classic/Tabletop/Round-based RPG is focused around class-driven, mechanic combat with almost equal focus on story. Examples would be Baldurs Gate 3, Dragon Age Origins, etc.
A story RPG is focused around immersing yourself in a story without that much difficult combat. Examples would be Kingdoms of Amalur: Reckoning, Skyrim and such.
Then there are J-RPGs, like Final Fantasy, that do both mechanical combat and story driven experiences.
Then we have Shooter-RPGs like Destiny, Warframe and Darktide, that have some RPG elements to it but mainly are straight-forward shooter experiences with (or without) story.
Rogue-like and Sandbox RPGs exist as well.
There are a lot. But when people speak of “RPG”, they usually refer to the classic ones. And in that regard, I would have to point more at WoW 2004 than WoW 2025. Sure, you could play WoW in 2004 to some extent alone. But that didn’t apply to dungeons and raids. You had to socialize and understand your class or else you were dragging down everyone else with you.
And the fact that people struggle with Dimensius on story mode, shows just how horrible some players in player skills are. I didn’t follow any mechanics on story mode from Dimensius and not even his strongest attack brought my HP, as a Holy Paladin, down to 92% HP.
It’s quite frankly, so sad that people struggle there. Also one of the reasons why I think that WoW wouldn’t benefit from a Matchmaking system for Mythic+
Like I said, it used to be the norm, but isn’t anymore.
See it like “the genre lost what made it unique to some” as a statement.
Same could be applied to Sea of Thieves. The game was designed with forced social communication in mind. People like me, that weren’t looking for that, simply were droven out of the game until the devs gave in and added options to not be forced to talk (such as text chat, pings, emotes, etc.)
There is even a No-PvP mode by now, something that was actively denied right from the start because they wanted the Seas to be dangerous both from AI and other players crossing your path as pirates.