It didn't try to do what you put on that list. It didn't do messaging; messaging programs used it. It didn't do backups; backup programs used it.
It's just a foundation-sort of program that does encryption and signing of arbitrary data, using one format for keys, and allowing working with those keys whether they're in the same computer or in a smartcard/hsm. That simplifies key management, since it allows you to have one Yubikey with your PGP key on it and do basically anything crypto related.
But what I believe someguydave was referring to was stuff like smartcard/Yubikey support, not different uses of encryption and signing.
age can't sign, though. It's not as useful. You can't use it for authentication, for instance. You need a separate program with a separate key and its own separate yubikey support.
I was more thinking of the extensive support GPG has in many email clients on many platforms for supporting encryption and signing use cases, as well as key management.
It's just a foundation-sort of program that does encryption and signing of arbitrary data, using one format for keys, and allowing working with those keys whether they're in the same computer or in a smartcard/hsm. That simplifies key management, since it allows you to have one Yubikey with your PGP key on it and do basically anything crypto related.
But what I believe someguydave was referring to was stuff like smartcard/Yubikey support, not different uses of encryption and signing.