Nobody is actually against immersion in games that tout massive persistent worlds, that would be silly. Besides, this is a genre that demands it to some extent. I'd wager, however, that some people are too focused on the idea. Sure, games like Final Fantasy XI and expansions like Wrath of the Lich King deliver a substantial amount of story -- but not above their unique mechanics.
Let's take this moment to talk about mechanics. The very name of the genre -- MMORPG or MMO if you like -- comes from the mechanics themselves. In fact, ostensibly, the best part of immersion comes from the mechanics of a game. What people get from a game like Fallen Earth in terms of story comes from its sandbox mechanics. On the other hand, walled garden games like Word of Warcraft or Aion enable the kinds of stories you see from generally any online game that deals in large enough player numbers.
If you're looking for more immersion, you're looking to kill a certain amount of game mechanics. Removing numbers from equipment sounds like a totally rad way to make an experience feel less "gamey" but ultimately players still realize they're playing a game.
And that's really the whole problem with the concept of immersive gameplay, it's such a subjective concept. What if immersion to me is having those numbers? What if those numbers validate my alternate, digital existence? I feel like the whole discussion is something of a dead end that ultimately gets us nowhere. Mechanics are at the core of every game; moreso with persistent world online games. Thus, to me, the debate isn't about how much immersion we should or shouldn't have, but how we can create an improved sense of immersion via new mechanics.
Let's go back to Wrath of the Lich King. That game had tons of immersion! Why was that again? Oh yeah, that new phasing mechanic Blizzard came up with and implemented in a clever way. Final Fantasy XI injects in-engine cut scenes into the main quests of the game, many of which involve your avatar.
I think the term we're looking for is probably Immersion Mechanics, although I'm not really a huge fan of coming up with arbitrary terms. Okay, maybe I am a little, but I know it's not really necessary. All I'm saying is that this shouldn't be an argument of which is more important. In fact, it needs to be an intelligent discussion of how to utilize the driving force of any video game -- mechanics -- in order to create a better and more engaging story, sense of immersion and ultimately improved gameplay.