What you are describing -- a system where I have to maintain accounts on a number of separate networks that don't interoperate due to content control disagreements -- is an ecosystem of competing centralized systems, not a decentralized one, and that people who run their own servers are reportedly presumed evil and defederated either by default or at the drop of a hat is a visceral demonstration that this setup undermines most of the benefit you think you are getting by calling it "decentralized". The reality is that many of the people using Mastadon would be not just "happy enough" but "actively happier" (per all the clearly ridiculous controversy surrounding people doing the supposedly-evil work of building search engines or, heaven forbid, being able to quote-tweet without permission, lol... if you are going out of your way to prevent hyperlinks, something seriously wrong has happened) using a centralized competitor to Twitter that was merely run by someone they liked.

The number of people who have to maintain more than one account is minuscule, and most of the time they ought to reflect over why they are part of communities with such mutual animosity that they can't find one home that accepts both/all.

I run my own, and have seen no trace of this being "presumed evil" you speak of.

Issue is that the admin is the one who decides what you can see. I remember a few months ago some meme/map or the network divided in "normie" and "weird" sides of the network. The impression I got is that the normie side instance admins apparently cooperate on blocking instances.

What if I want to be on both? Well you need two accounts.

Two accounts are trivial to manage, especially with a third party client. I managed more than that through a bookmarks folder. Many people have multiple accounts on various platforms anyway.

Also you could always host your own instance and be your own admin. I started doing that a couple of weeks ago. It's easy to find a host plan, if you don't want to do all of the work yourself. But you could still do that if you wanted to.

Then get 2. They’re generally free.

That schism is inevitable. To pick an extreme case, imagine a server for LGBTQ people and another for self-declared neo-Nazis. The people on the 1st might have very strong feelings that they want no contact whatsoever with people on the 2nd. There’s no world where it’s reasonable to say they have to keep their servers connected.

Now suppose you want to follow people on the 2nd server for journalism purposes. It’s unreasonable to have an account on the 1st server and then complain that they’re not talking to the 2nd. Even if you have legitimate purposes that aren’t creepy, they’re not going to go along with it. So instead, you get another account to follow the 2nd server and everyone’s happy.

The Mastodon server I own turned 7 years old today. We’ve blocked probably a couple dozen servers over the years. In every case I can tell you exactly why we blocked that instance. Most of them involve, literally, their users sending mine swastika imagery, death threats, or other utterly indefensible content, and the moderators of those instances being OK with it. My users stick around because they trust my explanations for the moderation actions I take. They don’t want to manually filter actual Nazi content from their timelines. Those that do can pick any number of servers that wouldn’t block that content.

What if I want something that isn't an echo-chamber?

Join one of the instances with looser moderation.

Suhh instances tend to be put on shared blocklists, effectively making them echo-chambers too.

I think that says more about the content of those instances being blocked. If you're transmitting content bad enough to get blocked by a large portion of the fediverse, the problem has more to do with what you're saying than their decision not to hear it.

The problem is the assumption that if you allow someone to say something on yur instance, then you necessarily agree with it.