I lived in apartments with not many play opportunities during my childhood, but virtual worlds provided pretty much that play environment for me (of course, with different risks and less whole body physical activity). The game was Tibia (it still exists), and it required a lot of planning, had all elements you'd want children to be immersed in, like:
in-game mysteries (is it possible to solve X or Y quest, get a certain item, and so on?), some of which persist today (probably the remaining ones can't be solved),
social interaction: you needed to trade with players for almost everything -- buying all equipment, even to use magic you were required to trade unless you could make them yourself),
in-game economy, mechanically, the game wasn't too hard, it was very well balanced; a big element was finding where you could be more efficient to sustain your own advancement through the game; trading was a major gameplay element,
making friends: for many, this was really the point of the game, just meeting people, talking for hours, finding where they came from (often distant countries I'd have no opportunity to visit); most activities greatly benefited from a group, although you could solo;
coordination: you needed a really good attention and coordination to play in certain situations; most of all, you needed to understand your capability and the requirements to make sure you didn't lose weeks or even months of progress (the death penalty was something like 10% of your total playtime!).
It's hard to overstate how much growth it afforded me and by brother -- the lessons are too numerous to cite, from interacting with people to managing risk on everything you do. We did recognize, even at the time though, that it could get us 'hooked' in a bad way -- and that the game was ultimately limited and there was a life outside (other activities) with a greater horizon. My brother just quit completely one day to never return; I always kept visiting the world out of curiosity and nostalgia. It really felt like having a wild virtual childhood. I still think about people I've met in that world some 20 years later.
Unfortunately, some of the aspects that enabled this experience have been degraded significantly. The greatest loss was probably due to cheating and bots. Cheating was already possible, maybe right from the beginning, but it took a long time to develop and become widespread. At one point though, almost every serious player was cheating, and a significant portion using bots to automatically achieve high levels with low risk (or just amass fortunes and transfer to "clean" characters). Seeing no great alternative, the developer (Cipsoft) started to understandably introduce the various cheating systems (automatic aiming and item usage, etc.) into the game itself, reduce death penalties, and so on. It also copied other games that have automated markets and so on, and for a while bots almost ruined the game (only much later they got a deal with BattleEye that significantly improved the situation -- but the game was already changed). The game now is much less wild and much more like a single player experience.
One very interesting aspect of the game is how much this wilderness is important but still very troublesome. The risk is what teaches risk management; but it also enables other player abuse. The possibility to kill and get killed was very scary (of course, maybe not as scary as many IRL risks), but it also built serious trust, when you had to trust your friend wouldn't turn against you for personal gain, find who to trust, etc.. It really showed what's ugly about humans at the same time as what's really amazingly beautiful -- some of the most kind and selfless people I've met were playing that game (and also a handful keen to set you back a long time just for pleasure). I think one way or another everyone that played it learned the value of cooperation in some way. I thought it was my yardstick of civilization to see if people would kill for fun when "it's just a game" (with serious in-game consequences for your victim) or act cooperatively -- I thought the ideal game was not one where you can't kill one another, but one you can, but almost no one does (I never subscribe to the notion that in game killing was "a fun part of the game" -- although I did see the allure of the loot; after all, not killing was also part of the game; in any case, you could always stop playing or opt for non-pvp servers, which most of my IRL friends did -- but I refused).
A very interesting experiment just in life, is the least I can say.
Note: There is a spiritual successor of the classic game going on in https://medivia.online/ Be warned -- this kind of game is as much of a time sink (and perhaps as addictive) as it sounds; but if you feel ready for this sort of experience, it seems still possible; I haven't ever played Medivia.