Nobody wants to live in a single shared virtual universe, hell most people don’t even seem to want to live in shared reality and have segmented themselves off into echo chambers on social media.
Second Life was supposed to be "Internet 3.0". All businesses would effectively have to have a presence in-world. Many large ones did. They're all gone now. The vision of doing things in a 3D world wasn't the right one.
SL still has about 2/3 of the users it had at peak, and is going along fine. About 35,000 to 50,000 users at any time, about even with GTA V Online. Sluggish by modern game standards, though, which is a big problem for new users.
Rosedale went off to do High Fidelity, which was supposed to be a better Second Life. It works, but it flopped. That company has recently "pivoted to enterprise", having failed with their consumer product.
Whether the Metaverse needs gameplay mechanics is an interesting question. It definitely needs game aesthetics. In High Fidelity, when you started up a new region, the world came up as a big piece of graph paper on which you could build. Rosedale thought "build it and they will come". They didn't. SineSpace had the same problem. Sansar (a Linden Labs project separate from Second Life) paid people to build good looking areas. They had a Star Wars prop museum, a Ready Player One prop museum... People came, looked once, and left.
Second Life starts new regions with terrain that has hills, streams, rivers, roads, and trees. Sometimes a full city road grid with street lights. Management behaves a lot like a municipal government.
Recently, Second Life opened some new areas of "Linden Homes". It's a nice suburbia, and it filled up so rapidly that additional areas are being added. It's developing a suburban lifestyle. There's no plot, but there are picnic and boats and pets and pubs. People hang out with their neighbors, drive around, set up community associations, and have barbecues. This appeals to people for whom middle class suburbia is an unreachable aspiration in real life, a growing demographic.
Considering the extremely high cost of SL land, i doubt this is true.
[1] https://community.secondlife.com/forums/topic/435890-oh-the-...
Plus the client feels like a something that grew organically out of a research project from the early 2000s and is about as new user friendly as Blender.
It's not impossible that a "metaverse" would benefit from the same network effects. You would want to inhabit the same (virtual) reality as your friends, probably, and they would like to inhabit the same as their friends, and so on. (Which doesn't mean we would like this outcome!)
Most social media tend to be extremely sticky, and not segregated by echo chambers. It's not like the socialists went to twitter, rightwings went to instagram etc.