Public keys as addresses would be great for the perfect user but for real people they can come with their own failure modes that are much more real concern than abusive governments for most users (especially since your government will always have ways to get to you):
- How do you deal with a private key being lost? You can't treat this as a "almost never happens" scenario so you need a way to find people's (new) public keys which will be subject to all the same threat models as current domains or any other addressing scheme: there will be some kind of central authority.
- How do you deal with private keys being leaked? Again, you will need a way to revoke keys without having access to the private key which again is only doable with an external source of trust.
- How do you deal with a private key being lost? You can't treat this as a "almost never happens" scenario so you need a way to find people's (new) public keys which will be subject to all the same threat models as current domains or any other addressing scheme: there will be some kind of central authority.
- How do you deal with private keys being leaked? Again, you will need a way to revoke keys without having access to the private key which again is only doable with an external source of trust.