Too bad that seems impossible to effectively implement at scale.
There are technical solutions to this. The old one was called hashcash, which a predecessor to cryptocurrency.
To get an account you would have to do something like $5 in electricity worth of computation one time, which you can do without giving anyone your name. But then if you do something foolish and get banned, it'll cost you another $5 (or however much is necessary to provide a sufficient deterrent) to get a new account.
Obviously now you could just have them pay (or mine for you) a small amount of cryptocurrency, which would then go to offset the cost of banning the spammers who still try their luck.
It's $5, not $500. Anybody using an account long-term will experience more cost from having it deleted than from paying that amount for a new one.
The reason it works is that a poor person gets to amortize that $5 over the life of the account, typically ten years or more, which makes it a negligible amount even for someone making minimum wage. Whereas the spammer gets banned and needs a new account every 90 seconds.
And if the problem is that your mods are imposing censorship on disadvantaged people, you don't want something that makes that sort of "moderation" effective. But that's a different problem. Maybe try not having such a small number of large platforms so it's easier for people to abandon the ones doing such things.
That is the problem. It's an unsolvable problem for the near+ future - unless we shift so much power from the public to the powerful that they can silence the public on a whim.