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.
Well, the vast majority of people who came here about a year ago from Reddit did so explicitly because of the 3rd party app situation (and many of the app devs came as well), making apps a massive priority for Lemmy as a byproduct. As a direct result, we have tons of options for the size of the platform (I believe iOS has about a dozen apps/PWAs and roughly the same for android, and afaik only 2-3 of them cross-platform).
It’s probably fair to say most of those individuals are still using the apps by default if they are still on Lemmy, even if you don’t see how that’s desirable. And they are an option for new users as well who haven’t gotten used to any of it yet.
So the issue you are talking about is not solved by apps with multi-account support, because we’ve had that for a large portion of users for many many months. The people who would be creating secondary and tertiary accounts are going to do that anyway. Plus it’s not like it’s difficult to navigate to a different webpage on web and sign in to that. I manage my account stuff on the web versions of my instances, and never had a problem getting between them. You could probably even have multiple accounts logged into multiple tabs without issue (I haven’t tried, so unsure)
I’m on a smaller instance because I wanted to be. I have another account that I made before this on a large instance, because I didn’t understand the fediverse or instances, or how to find one. People mostly start on larger instances because they can find them (the apps have lists of default instances to sign up with, for example, which are mostly bigger ones), and most stay there because it’s easier. Sometimes they get sick of the drama or the issues and move somewhere smaller like I did. They actively want to be on a smaller instance, whether because they understand the value of spreading out or because they just don’t want to be on one of the big instances that causes drama or whatever.