It's definitely trying to be user friendly enough that non-technical users like the family members you mention can use it to replace passwords. For your use case with a strong password and 2FAS to generate a code, it still gets rid of the phishing potential. The main advantage for the other people like your family is that they don't have to type or autofill anything, just select an account to log into or click approve on their phone. A main advantage for the service is that the user's diligence is taken out of the equation for a lot of it and they don't have to worry about a user giving their password and 2FA codes to a phisher. If a user tries to use a passkey at the wrong site (like a phishing site), it won't pop up as an option to select because the domain is wrong.

Passkeys can also help anyone who is using a service in an indirect way. The 23andMe "breach" was due to stolen credentials from other actually breached sites being used to log into accounts that have data shared with them. That 23andMe data was shared to those compromised users by people who may have actually had all their security turned up to the highest settings like 2FA but was nonetheless scraped and obtained by the bad actors anyways. If 23andMe had been using passkeys (or even magic login links in an email), there would have been no credentials from other sources to use against their 23andMe's users. Moving everyone to more secure authentication methods is in the best interest of everyone involved, it's just that typically it was a hassle to have to setup an authenticator app or a password manager for 2FA. Passkeys, when everything is working properly, finally provide both more security and more convenience for the average person than just a password and so people might actually adopt them.