It’s not quite that bad. I ran my own mailinabox server on a vps a few years ago and didn’t have much issues with spam lists. Only gave up because I couldn’t be bothered updating the thing.
That's the death of all decentralized systems, it's too much work in the long run.
They work great when they're the ONLY option in town, but eventually people centralize on one aspect of it, as they did with email.
Email used to be so decentralized that it was literally run on your machine (not your terminal, which was dumb, but the machine the terminal connected to) and even a single company department might have 10+ machines that could receive email (email addresses would look like name@machine.department.company.com).
Then it devolved to one per department, and then one per company, and now one per massive IT provider.
Security became big as well. Mail servers used to get hacked constantly and you’d have your private data leaked and your server turned in to a spam gun.
These days to host anything securely you need a team of the top minds in that domain working full time on it. Just makes no sense to run your own mail server when for less money you could let someone else do it and they will do it much better.
This is just a sign of the industry maturing imo. You could relate it to construction. Used to have people building their own mud and stick huts but now everything requires planning, regulation, codes, licensed workers, etc.
