The psychology of this problem is that users are too lazy to maintain multiple accounts when all they have is Lemmy’s stock web client. So they choose one of the big nodes: lemmy.world, sh.itjust.works, lemm.ee, lemmy.ca, etc.
These Cloudflare-centralized nodes are able to greedily exploit the #networkEffect because due to lack of multi-account software. If there were some well-made 3rd party client apps for Lemmy that would be designed for multiple accounts, then more users would be willing to create accounts in more decentralized parts of the fedi.
Mastodon somewhat proves this because the client-side tooling is in place to make it convenient to have 6 or Mastodon accounts. And Mastodon nodes are better balanced.
I'm using the eternity client (a fork of the infinity client for Reddit), and even though development has largely slowed down, it supports the features I need as a "normal user" (not as a moderator) of the threadiverse. And it supports multi-accounts quite seamlessly imho.
As a Debian user I tend to work close to the ideology of using apps from official Debian repos. Debian is quite popular but also disciplined with a quality standard. So an app’s inclusion in the Debian repo somewhat reflects a level of maturity that puts a project on the radar to be taken seriously. There are currently no threadiverse apps in the Debian repos.
Some would say generally that no non-Debian app is worth looking at. But I do make some exceptions and might have to take a look at Eternity despite the opening sentence: “Eternity is currently in the early stages of development. Expect many unfinished features and bugs!”
I don’t think those figures are trustworthy. I recall a page that tracks user counts which named some server I never heard of with a count an order of magnitude higher than lemmy.world. Might have been lemmyverse.net, not sure.
Counting active accounts is a bit tricky I can imagine. So I judge by looking at the activity. Lemmy has ghost towns and 1 person communities which appear from the timeline like an announcement community but in fact they are open discussions where hardly anyone participates except the moderator. These are not niche topics either. It’s because users only want to manage one account. The stock web client dominates, which is inherently a one-account client. So the single most popular app fails to resist the gravity of the giant nodes. There is a paltry selection of 3rd party apps. Nothing in the Debian official repos.
I went to phtn.app and just got a 500 error. So whatever that is, it’s probably not a significant factor here either way.
In Mastodon threads I see more diversity of nodes people are coming from. Whereas when reading a quite active Lemmy thread you see something like 90% of comments coming from the top 5.
Every node has a different set of relationships to other nodes. If you create only one account and you choose a small low-activity node, you’re isolated by which nodes are federated and defederated to that node. The front page timeline is also limited by the subscriptions of others on that node which narrows what’s exposed to you. And worse, because most of the population has disregard for decentralization, those subscriptions are mostly to communities on the biggest nodes which exacerbates the imbalance.
It’s good for the decentralization principle to avoid the large nodes¹, but doing that bring isolation and limited exposure. So to counter those problems you need accounts on multiple small nodes.
¹ This means not only avoiding having an account on the large nodes but also avoiding communities hosted on those giant nodes.
Otherwise I don't see that as a problem, it's just like forums with the addition that you don't need an account everywhere. You can participate everywhere. There are also good searches for communities.
Why would you need more than one account? I'm on a single user instance and only have this one account and it works just fine I can subscribe to which ever community on whichever server and can see all comments and everything. What would I get from having more than one account on smaller instances?
Self-hosting is a different scenario than the way most users reach the fedi. Self-hosters certainly have fewer reasons to have multiple accounts. But obviously the one unescapable reason is privacy. If all activity is under the same account, doxxing risk is pegged.
Another reason a self hoster would want multiple accts is followship. Someone might want to follow you because they love your French posts about oil painting, for example, but since you do everything with the same account they also have to see posts in English about politics, religion, phones, movies, etc, they may not want all the other noise. Compartmentalisation improves followship.