I think the point is that Microsoft is phasing out AD and Exchange by making the licensing costs prohibitively more expensive than just using their cloud identity, mail, and SaaS services.
We are still on prem for AD but that’s due to legacy software that requires it and will be that way for a while but cost will eventually have us on a cloud identity provider and it will probably be Azure
We already are on exchange online, the costs just don’t make sense to host exchange on premises unless you have a legacy reason too.