People lose their gmail accounts all the time for weird reasons. Maybe you are specifically talking about a world where everyone self hosts their own servers?
If email was better designed, it would not allow these situations to happen. For example, if server operators didn't own your account, there would be no problem.
Only solution is something like how Farcaster does it where you at least get to keep your public key the same and usernames are optional.
https://github.com/farcasterxyz/protocol#3-identity
Or go the urbit route and make the addresses totally user owned.