I was going to agree completely but I think there's a use-case where age can work sensibly; distribute separate public keys to each semi-trusted host to perform

I was going to agree completely but I think there's a use-case where age can work sensibly; distribute separate public keys to each semi-trusted host to perform its own automated backups. Rotate the keys frequently. There's still a significant advantage over symmetric encryption; the backups themselves will never be readable by an attacker who compromises a semi-trusted host. The reason this scenario makes sense is that even if backups were encrypted and signed with gpg an attacker gaining root access to the semi-trusted host would also have access to its signing key and be able to impersonate it anyway. By only accepting backups from particular hosts based on its currently-valid public key we can avoid the risk of an attacker overwriting arbitrary backups. You're going to be rotating either a gpg signing key or an age public key frequently regardless to reduce the time window when a potential attacker can impersonate a host, so age makes things slightly simpler by avoiding signatures entirely.