The statement "SSH keys are just long passwords" in your linked post is a huge red flag that you don't understand enough about how they work and are in no position to dispense advice (that anyone sane should heed) on the subject.
To start (but it would be a longer discussion), passwords can be captured as you type them into a compromised host, SSH keys can't. Also SSH keys can reside on a security device (TPM, smartcard, HSM, security token, whatever) and this way they can _never_ be captured, barring exploits on those hardware devices, even if your workstation is compromised. Some hardware security devices have features like touch-to-authorize, or even biometrics, for every single usage. SSH keys can be _used_ while unlocked, but not from a compromised remote site (unless you do agent forwarding, which this article is all about), and never captured from there. Passwords have literally _none_ of the above features.
Forwarding usually bad. SSH Keys otherwise good. Passwords so bad they're not worth comparing to anything.
(and yeah, there's stuff even better than SSH keys)
To start (but it would be a longer discussion), passwords can be captured as you type them into a compromised host, SSH keys can't. Also SSH keys can reside on a security device (TPM, smartcard, HSM, security token, whatever) and this way they can _never_ be captured, barring exploits on those hardware devices, even if your workstation is compromised. Some hardware security devices have features like touch-to-authorize, or even biometrics, for every single usage. SSH keys can be _used_ while unlocked, but not from a compromised remote site (unless you do agent forwarding, which this article is all about), and never captured from there. Passwords have literally _none_ of the above features.
Forwarding usually bad. SSH Keys otherwise good. Passwords so bad they're not worth comparing to anything.
(and yeah, there's stuff even better than SSH keys)