I'm with 'sillysaurus3 on this one: I have no interest in using a site that only uses the likes of Facebook and Google for authentication.
You've just listed four good reasons to reject centralisation of credentials with those organisations, and any one of them would be sufficient disincentive in my case.
I can think of at least one more good reason: If I'm dealing with an organisation, particularly one I'm paying for their services, if I have unique credentials with them, and if anything goes wrong on their side, then it's going to be their responsibility to fix it and make good any damage. If I'm dealing with them and using a third party for credentials, and that third party gets compromised in some way, then it seems likely it will end up being my responsibility to sort everything out and pay any related costs.
You've just listed four good reasons to reject centralisation of credentials with those organisations, and any one of them would be sufficient disincentive in my case.
I can think of at least one more good reason: If I'm dealing with an organisation, particularly one I'm paying for their services, if I have unique credentials with them, and if anything goes wrong on their side, then it's going to be their responsibility to fix it and make good any damage. If I'm dealing with them and using a third party for credentials, and that third party gets compromised in some way, then it seems likely it will end up being my responsibility to sort everything out and pay any related costs.