NT underlies the majority of M365 and many of the major Azure services. Most F500s in the US will have at the very least an Active Directory deployment, if not other ancillary services.
IIS and SQL Server (Win) boxes are fairly typical, still.
I am not suggesting NT is dead on servers at all. I am positing it would be dead had it not been for owning the majority of desktops. Those use cases are primarily driven as an ancillary service to Windows desktop[1], and where they have wider applicability, like .NET and SQL Server, have been progressively unleashed from Windows. The realm of standalone server products were bulldozed by Linux; NT wouldn't have stood a chance either.
[1]: In fact, Active Directory was specifically targeted by EU antitrust lawsuit against Microsoft.
For all large corps, users sit at 1990s-style desktop computers that run Win10/11 and use Microsoft Office, including Outlook that connects to an Exchange server running on Windows Server. I'm not here to defend Microsoft operating systems (I much prefer Linux), but they are so deeply embedded. It might be decades before that changes at large corps.
That was true once, but not true now. On-prem Exchange is rapidly being squashed by Microsoft in favor of 365. The direction of travel for the Outlook client is clearly towards web (I note anecdotally that the Mac client, always a poor relation to Windows, is so laughably clunky that the Mac users I know forgo it in favor of the web client.) If the service is in the 365 cloud and the client is a web browser, who needs Windows for this discussion? We might end up in a future of terminals again for the worker bees and 'real' computers only for the people who need Excel and Word and for whom the web versions dont cut it
IIS and SQL Server (Win) boxes are fairly typical, still.