For what reason? Email these days is basically just a machine for marketing and identity verification, and the latter can be done better by other solutions
Plus, despite the fact that email is designed to be open, it has been perverted by big tech into an effectively closed system, as your post makes reference to. I see no real reason to keep email going, when a better less centralized system could be built to replace it.
Yes, that's true, but most people aren't going to host an email server, because it's a pain(I know, I administrate 3 of them), which means that Google, Apple, Microsoft, Proton, and the other big tech companies will always control the majority of email accounts, and that gives them effective control over the entire network. Our ability to self host servers outside of big techs bubble doesn't make the bubble go away.