"As such, if I stand up a new email server and start sending email to Gmail addresses, I am at the whims of Google deciding what email from me gets delivered."
This is the critical point. Adoption matters, and always ends up with consolidated power. It's just how things are, and how they stay, short of the severe intervention of dramatically easy-to-use tools for "click to host your own stuff".
This is the critical point. Adoption matters, and always ends up with consolidated power. It's just how things are, and how they stay, short of the severe intervention of dramatically easy-to-use tools for "click to host your own stuff".