That is not really the problem, that is the symptom. Making it redundant makes the factor property moot. And while it might be hard to replace, it's not irrepla

That is not really the problem, that is the symptom. Making it redundant makes the factor property moot. And while it might be hard to replace, it's not irreplaceable. One issue is that if you have 60 TOTP accounts on an app on a phone and you desire to replace it you'll end up with a keyring full of FIDO keys. Those are just as 'non-redundant' and 'irreplaceable' as the phone was. The problem that causes the symptom is pass-the-audit mentality in the implementation of MFA. You have many options to make this "better" like picking any push, FIDO, U2F and TOTP method at authentication time. Lose 3 of those and you still have one available for the normal flow. And then there are backup codes that most people don't actually print and store because for some reason they are either unaware of it or believe that it will never affect them.