I seemed to touch a nerve to even imply Microsoft ever has compatibility issues…

Yes, you can get “modern” and give Microsoft continual money, yes, that was the whole point.

As to no alternatives, well, there are. FreeIPA is pretty squarely an Active Directory equivalent. The challenge is that if you have both Microsoft and non-Microsoft infrastructure, you have to use Microsoft management for both because Microsoft will only interoperate with the Microsoft solution. Once you have any Microsoft, then the only option for an all encompassing solution gets automatically locked down to only Microsoft.

Since you probably are employed by Microsoft or a Microsoft focused business partner, your perspective may be a bit skewed.