There's 2 things to consider.
First since this is all relatively new there's a bit of a gold rush for starting communities, eventually a couple of major communities across instances will emerge for different topics and those will stick, this will make things a bit less impractical from the point of view of an average user.
Second is if we ever get functionality on lemmy to create the equivalent of a multireddit, where you can group as many communities as you want into a single curated view (either for yourself or shared to the instance) then this becomes a non-issue.
Fediverse and the internet in general is already the metaverse. All we need to make it look like in sci-fi is for majority of users to interact with it in a 3D virtual space instead of 2D. XR technologies will get us there eventually but content on those platforms is lacking at best and is very far from general adoption.
The next big hurdle is large corporations trying to "create" the metaverse, which already exists, and control it. Which basically disqualifies anything they are doing from ever being the metaverse. I actually felt some degree of rage when facebook renamed themselves to meta, they single-handedly ruined public perception of the concept, anyone talking about it now in the general public is not taken seriously.
What's also missing of the metaverse right now is owning your identity and taking it with you everywhere you go, fediverse comes close to that concept but is far from perfect since it's pretty hard to interact with other fediverse technologies right now, if I'm on lemmy I don't see any way to consume/interact with mastodon content or kbin content. However being able to traverse every instance of lemmy out there using one account, hosted on a server run by myself or someone else is a start.