It's not. Support is about on par with Google for SMBs. I had a client get locked out of the admin panel for about 2 weeks before getting through with support.
The difference is that everyone's account kept working during that time so business kept on as usual, just the admins couldn't change anything.
The sad thing is I don't think anyone did anything unusual and it was some kind of bug of Microsoft's end.
Good to know. I'm only dealing with 7 M365 tenants regularly and we have "break glass" accounts in each one (not tied to Customer's SSO, MFA unrelated to other admins, email address outside the tenant) to try to minimize the possibility of getting locked out, but I know it's always a possibility.
Moving the MX for the domain and limping along from backups is my worst-case contingency but given that there's no place other than M365 to restore the backups to it isn't a very good strategy.