Cross Server dungeons/raids had the exact same consequence. In the early expansions you would play with people and get to know them. Sometimes you'd be levelling at a similar pace and cross paths on a few of the instances/quests. Maybe you'd get to chatting?

I know we recruited several people into a casual guild based on doing a few dungeons and getting on well with them. This was, ofc, before guild perks etc gamified that aspect in a shitty fashion.

Ofc you also got to learn people you never wanted to instance with again. Reputation mattered! As the Parent said, may as well be playing with NPCs.

Everybody talks about this part with rose colored glasses and nostalgia, conveniently forgetting trying to put a group together for a dungeon and spending upwards of an hour before you even start, not even knowing if your team members are good enough.

I certainly don't have the time to spend on that sort of thing, so if it weren't for things like dungeon finder I wouldn't even play the game anymore. Same with other games, if there wasn't any matchmaking I probably just wouldn't play.