You have choices now, whereas before you had basically one.

Yubikey offers you a hardware device specifically for this purpose. It can't be copied and it really is the definition of something you know and something you have. It has pros and cons, one of those cons being that if you want to use them you are stuck having multiple devices, one for a backup.

Don't like that con? Well, play the game a little and you have additional options coming. Such as the solutions from password managers and platforms like Apple and iOS. Add your sites in a password manager and it'll sync between devices, you basically only have to add one single thing (your password manager) and as long as you have password manager access you can sign in to those sites anywhere that your password manager is available, and where it isn't you gain the QR code passkey option that is being added.

You can mix and match this to your hearts content. Want to use a Yubikey as a backup? Add the device to your sites, stash it away where necessary. Yes, the con of having to add it to each site is still there but it is an option. Want to use all of these? Sure can. Add your iOS device, your password manager, and your Yubikey.

Want to only use one? Just add that device. But you might be foot gunning yourself without backups depending on which you use.

Stop being difficult and just use your head a little.