>Mastodon users praise it for somehow being “better” than other social media yet the whole “pick your subculture’s instance” thing really closes you into an echo chamber way easier.

That's exactly what makes it better. People keep saying "echo chamber" as though having rules and standards is a universal negative but their definition of an echo chamber is just any platform that doesn't want to deal with their bullshit. Fine, it's an echo chamber. Go make your own with blackjack and hookers if you don't like it.