If a process has the privileges to run as a keylogger, it can also grab your local SSH private keys and possibly harvest passwords and passkeys from your local password manager vault [1]. The process has local access and since it is a key logger presumably your master password. (The complexity depends a bit on the password manager, e.g. IIRC macOS keychain always requires a roundtrip through the secure enclave).
Honestly, if you are anything other than a casual user, and don't have devices with support baked in already, it's crazy not to spend ~£60 on a pair of security keys for passkey/U2F. It's not a lot of money and is just so much more secure.
100% this. A secure enclave or a hardware key is the only way to keep your key material safe.
Also, app sandboxing should be the default. macOS App Store Apps are sandboxed. Unfortunately, these days the standard is still for applications to have unfettered access to a user's files.
[1] Passkeys can also be on a security key, but e.g. Yubikeys only have a small number of resident key slots and I think passkeys to most people means key material synced through iCloud/1Password/your favorite cloud.