Why wouldn't that be a good thing? I don't want my apps breaking just because the OS updated.

Not disputing the obvious advantages, but since you asked:

Being forced to maintain compatibility for all previously written apis (and quite a large array of private details or undocumented features that applications ended up depending on) means windows is quite restricted in how it can develop.

As a random example, any developers who have written significant cross platform software will be able to attest that the file system on windows is painfully slow compared to other platforms (MS actually had to add a virtual file system to git at one point after they transitioned to it because they have a massive repo that would struggle on any OS, but choked especially badly on Windows). The main cause (at least according to one windows dev blog post I remember reading) is that windows added apis to make it easy to react to filesystem changes. That’s an obviously useful feature, but in retrospect was a major error, so much depends on the filesystem that giving anything the ability to delay fs interaction really hurts everything. But now lots of software is built on that feature, so they’re stuck with it.

On the other hand, I believe the Linux kernel has very strict compatibility requirements, they just don’t extend to the rest of the OS, so it’s not like there’s a strict rule on how it’s all handled.

Linux has the obvious advantage that almost all the software will have source code available, meaning the cost of recompiling most of your apps for each update with adjusted apis is much smaller.

And for old software that you need, there’s always VMs.