No, I literally had to rotate keys because of this yesterday.
I think you can't fully trust them as long as broad cat commands (or similar) are used. It's really easy to accidentally read the wrong files.
Haven't tried it yet but https://fnox.jdx.dev/ sounds promising with…
True but don't mix this up with some sort of cloud service. You can host the secrets anywhere (S3, Azure Key Vault) or even put the encrypted secrets into the repo.
The base functionality could probably be replaced with a simple shell script and gpg