Windows has a lot of legacy components, because there's this Fortune 500 corporation which still depends on it in 2023. Say what you want about Windows, but its backwards compatibility is unmatched. Windows also had 32-bit x86 CPU support until Windows 10, meaning that it could still run some 16-bit Windows 3.0 apps.
Windows is also a clusterfuck of spaghetti code that only the most masochistic person would want to tackle. There's so much legacy stuff in there it's ridiculous. For example you can't name a file com because of the DOS days when a COM file allowed you to access the Serial ports.
This bothers me a lot and also applies, to some extent, to MS office software. If you go deep enough you end up in the same old clunky UI that actually did the job.