Once upon a time I believed that CP/M would never die. Then I believed that AmigaDOS would never die. Then many people believed that WordPerfect (which than ruled the small computer word processing universe) would never die (it hasn't, it's still there, but you have to look hard to find it). There are many people who believe that Microsoft/ Windows will never die.
The computing world is just like the biological world. There is constant evolution, new things coming up, old things dying away.
The dinosaurs were dying out before the meteor ever struck. It didn't look like that, but the evidence was there if you looked properly.
Now re-write the above paragraph, but replace 'dinosaurs' with 'Windows'. The evidence is there if you look for it.
Active Directory won't go away soon, but with governments adopting RHEL for its server platform, new versions of Linux supporting AD, and with LibreOffice outshining MS Office in most areas, the only thing keeping Windows and Office going is momentum. Our own Australian Federal Government has found that Outlook is very insecure, and open to malicious emails in a way that Thunderbird and Evolution aren't.
Linux is the equivalent of the small, burrowing mammals 250 million years ago, Microsoft is the equivalent of the reptiles and Windows is the dinosaurs(large, dominating the landscape, out of date). We are now just waiting for the digital equivalent of the meteor.
Microsoft won't disappear, just as the reptiles haven't, but Windows is on it's last legs. Whether it dies with a bang or a whimper we have yet to see.
Apple has long realised that if you create and manage the whole ecosystem (hardware and software) and have many parts of that ecosystem (different operating systems, different hardware platforms), you will survive any local disasters.
Microsoft has been exploring that, but only to a very minor extent. They tried to make phones, but that fizzled. They now make laptops, and are experimenting with putting their OS onto ARM architecture (Win 10 on a RPI4, anyone?) and with folding Linux into Windows. They have been trying the concept of putting all their users onto a subscription basis, but there has been some push-back from customers, and they will be offering one-time purchases of Office again next year. However, Microsoft hasn't really committed to providing a wide-ranging group of user-friendly products.
Microsoft is a very limited ecosystem. To most, it only has Windows and Office.* These two are like the Tyrannosaurus and the Brontosaurus** wandering along side-by-side. Nothing wrong with either, both perfectly functional, both dominating the ecosystem. For now...
* Yes, I know it has many more products, but any company survives or fails on its public image. This can be manipulated to some extent, that's what advertising is for. But, MS still appears to be a two-product family. That's not diverse enough for long-term evolutionary survival.
** Once more for the pedants. Apatosaurus is a nomenclatural synonym for Brontosaurus. You can use either. I grew up with Brontosaurus and I'm going to continue using it. (I know that by making this statement I am being a meta-pedant. Cope with it.)