They're not really doing the same thing but you're probably correct that most customers are just relying on AD. I can easily imagine MS beefing up their identity offering to be more on par with Okta.
We replaced Okta with Azure AD. AAD had better OIDC and SCIM support along with being _significantly_ less expensive -- plus we had to use it anyways due to M365/Azure, so Okta offered no value.
