We need something better than email.
Say everyone agrees and the entire world swaps to some alternative. Email 3.0 or whatever.
Wouldn’t we just have the same issue? Any form of communication protocol (that can be self host able) will get abused by spam. Requiring a lot of extra work to manage.
Setting up a web of trust could cut out almost all spam. Of course, getting most people to manage their trust in a network is difficult, to say the least. The only other solution has been walled gardens like Facebook or Discord, and I don’t have to tell anyone around here about the problems with those.