How many people do you know, that are able to properly use GPG (i.e. understand the pitfalls of misconfiguration, subkeys, key verification,...)? TBH, I believe the GPG ship has sailed a long time ago, even within the IT community.

Using Email does help in what way? Most people do use Mail , Gmail that is. Do you mean Email as a protocol in opposition to Whatsapp, FB Messenger?

How does not hosting on the major hosting providers solve the problems of walled gardens and filter bubbles and the closed internet? That's just ephemeral infrastructure.

Login integrations can make a lot of sense. I don't really see how not deploying integrations will protect us from walled gardens.