VR has fundamental usability problems. If you and the world move separately, people get disoriented. Most of the successes involve a virtual world locked to the physical world (Beat Saber) or where the player sits in a vehicle. Still, there are dancers using VRchat with full body tracking, the closest thing yet to full dive.
AR, in some ways, has more potential. In AR, people can still see where they are. It's mostly a hardware cost problem. If you could get AR goggles down to swim goggle size and selling for $39.95, you could do Pokemon AR.
I'm interested in big virtual worlds. Lately, that field has been invaded by the Make Money Fast / NFT / ICO crowd. They've been building crappy virtual worlds with overpriced virtual assets. I'm not sure how this ends.
Second Life has found a new big success. They added an area of "premium homes" two years ago. If you sign up for a paid membership, which is about $100/year, you get a nice upper middle class American house in a nice neighborhood. The neighborhoods are well laid out, nicely landscaped, and have several distinct styles. You can decorate your house, invite people over, have parties, visit other people, walk or drive around, or just hang out in your house. They've built over 60,000 houses so far and are struggling to keep up with demand. The neighborhoods are all hand-built, not just stamped out from some template.
These are planned unit developments in a virtual world. It's something people stuck in some crappy apartment want - the American Dream. [1]
This isn't the only option - you can buy raw land outside the planned unit developments and build your own thing. But many people just want to buy a nice virtual lifestyle. Something nobody seems to have anticipated is that there's a market for rather boring virtual worlds.
[1] https://youtu.be/2peH7aeuwPI