To be fair, the authentication for Microsoft is far more complex than any other comparable system. They have to deal with their own Microsoft accounts (Outlook, Live, Hotmail...), federated domains (via ADFS or third parties) and domains hosted in 365 too - Some of those being synced passwords from AD, some of those using pass through authentication from local servers...
Google just has to deal with accounts with Gmail domains and third party domains that they host.
Google just has to deal with accounts with Gmail domains and third party domains that they host.