What comes to mind when you think of a poor half-baked Microsoft product? You'd think Windows Me... except it was somewhat innovative in some aspects and is even more stable than 98 when you disable certain components (statemgr and pchealth). Or, Windows 8 (call me weird but I like the Start screen...). In reality, the worst operating system Microsoft made is Windows 11.
Let's start with their planned obsolescence tactics. They have recently removed Intel 8th, 9th and 10th gen CPUs from Windows 11 eligibility, more like they couldn't fix the flaws with DWM hogging up the resources on said CPUs. Many consumers just throw their laptop away when it doesn't receive updates anymore and just buy a new one, and Microsoft is well aware of that.
Now, here comes the user experience: Fluent design (in my opinion) is an insult to the years of research Microsoft sunk into making responsive and intuitive user interfaces, and the Start menu in Windows 11 has a horrible layout. And what's the point of combining taskbar applets into one? They're not even trying to distinguish themselves from macOS (except macOS did things right as unlike Windows 11)
This is more of a niche thing to talk about, but the File Explorer. Instead of documenting DirectUI APIs, Microsoft abandoned it in favor of XAML when Windows 10 was in development, and today we're seeing the effects of such decision. They built half-baked XAML islands on top of File Explorer's DirectUI-based interface and now File Explorer is a sluggish and buggy mess.
They could've spent more money on fixing the NT kernel's internals (many of them haven't changed since NT 4.0), or polishing up their UX instead of blowing their budget on AI and marketing ads.
It's safe to say Microsoft's last good employees have given up and Windows will only go downhill before things will ever improve.