Depends how you approach it.
If you’re just playing WoW and not doing anything else or communicating about anything but doing something in WoW, yeah, acquaintance might be a good enough word. More of a “work friend” kinda situation I guess. Not trying to equate WoW to a job, but that’s the level of closeness in that situation I think.
But I’ve always had those types of friends, and then another group of friends that I actively talk about literally anything with, play other games with, watch movies with, send mail to, etc.
Pretending the latter group aren’t “friends” seems weird to me. But maybe you’re not looking for that to begin with so you only end up with the former and that’s why you see it that way? Idk.
But anyway, people with your mindset are why people end up with “friends” that have been offline for 6 years with no communication. I mean, other than the obvious “They died” possibilities. Turns out its pretty easy to just disappear when you’re done with the game if you view everyone you interact with on the game as an acquaintance at best. Not a dig at you btw, just something to note. There’s always been people who separate IRL and Online interactions and people who don’t.