I'm pretty new here. I'd say the concept is the same in the sense that they are each their own community run by their own moderators. However, the all powerful Admins are those in control of the instance.
One interesting example is that Beehaw has started making "Bee themed" community icons which makes it easy to tell when you're looking at one of the communities hosted on their instance.
Someone on Lemmy.world could have another community with the exact same name, you just have to pay attention to the end (and having themed icons also helps).
But it goes even a little farther than that. We can end up with Mastadon (twitter equivalent) users who are also able to comment in these communities. I don't think its working in reverse yet (at least not for Lemmy.ml accounts).
You have to remember that this game came out a long time ago, it had many features at the time that set it above other games.
It had a good storyline, multiplayer, maps that would change every time you logged in (multiplayer), the ability to be powerful after spending a lot of time in the game (and if you saw anyone with a rare/cool looking armor you know they worked for it, there were no lootbox mechanics where you could just pay money for it). And of course... there is no cow level ;) The skill tree allowed for tons of different abilities and combos, or you could grind away at a single skill and become godly with it.
You may not recognize the appeal to the game now just because so many of the mechanics have been copied and implemented in countless other games since then.