I'm definitely not a fan of forcing anyone to use their (personal) phone for MFA for accessing company resources - I wouldn't really consider it a single point

I'm definitely not a fan of forcing anyone to use their (personal) phone for MFA for accessing company resources - I wouldn't really consider it a single point of failure though unless it was so poorly set up that there was literally no alternative log in method in the case of a lost/forgotten/broken phone. And if that happens it's the company's loss not mine - yes I enjoy my work and don't like letting my team members down but I can happily find other things to do if I can't access the systems I need to work (and they're going to pay me either way).