I mean...the entire period before the industrial revolution and the advent of modern medicine?
Some guy living in 1000BC China is probably going to be as well off as someone in 1000AD China, which is to say they both aren't well off at all. I'm not sure what you're trying to get at here.
Plenty of them are still at Blizzard, though OSRS did a good enough job of having new staff and still sticking to the original game's design philosophy. It's really not an issue, it's easy to see the bounds of how the game could expand within the original design philosophy.
For example, no LFG, keep the level cap, no transmog, no multi-server sharding, no removing RPG elements like hunter ammo, things of that sort.
Runescape 3 has been on its own development path since 2007. In 2013 they released OSRS, which has its own development path that sticks to the old design philosophy rather than the one that they took in Runescape 3 following the evolution of combat update.
Content in Modern WoW has an entirely different design philosophy than Vanilla. If they added to Classic, say 6 months to a year after Phase 6/Naxxramas has been released, that new content could stick to the Vanilla design philosophy and be totally warranted. They could even implement horizontal progression paths that don't invalidate Naxxramas as a source of powerful gear.
If necessary, they could also leave up a museum server up for certain players who just want to relive 1.13 over and over again.
I mean that's the case for you, but not for everyone. I've made connections in games (friends, guildmates, clanmates), that have lasted for over a decade. I don't regret a moment of the thousands of hours I poured into online games.
Some guy living in 1000BC China is probably going to be as well off as someone in 1000AD China, which is to say they both aren't well off at all. I'm not sure what you're trying to get at here.