> And if you then get rid of passwords, you are down to one factor

I agree this is a bit of a shame. I'm hoping platforms support using passkeys with other factors.

> You had better not lose your phone

You can sync passkeys between devices and backup to a cloud.

> big companies can't agree with each other on how to do this

This was the case 18 months ago, I'm not so sure it is anymore. On my Google account I can setup a passkey passwordless login with a 3rd party password manager. I can do the exact same thing with my Microsoft account. There are still rough edges, for example to setup the passkey on MS I had to select the method "Use your Windows PC" but it all works.