The service you propose will either have the same problem as google, be vulnerable to social engineering attacks (like phone number providers), or be tied to extremely expensive infrastructure (e.g. enable post office or DMV offices to validate identity for the purposes of managing access to this account).

Even if google had customer support agents, what do you want them to do in cases like this? They can't actually validate anyone as the owner of an account, they'd simply be the targets of people begging to access accounts.

Edit: the implication being, we probably simply need most people to just not depend on email for anything important. Unless you can maintain multiple 2FA methods, your email account isn't reliable enough to be trusted with important things.