Mostly referring to the release of the latest WoW extension which isn’t discussed anywhere (or maybe I missed it)
Many might have also played Guild Wars 1 which had a lot of that content you could only access with a certain minimum party size from what I remember.
Oh yeah GW1 was harder at launch because you only had limited NPC support, but the later expansions really expanded that (no pun intended) by adding more robust npc Heroes that could join your party and be customized.
Though GW1 came out 19 years ago, so a good chunk of potential GW2 players were in diapers when it came out. Gosh, I’m so old.
GW2 is very “solo” friendly. I put solo in quotes because there will typically be other people around, but you don’t have to talk to them or wait on them for most stuff. Like, earlier I was flying around one of the maps doing a little quest thing, and I joined in several events to fight monsters with other people. Didn’t say a word. It’s all very seamless.