I wholeheartedly agree. While the technical underpinnings of today's desktop operating systems have never been better (we have come a long way from DOS-based Windows and the somewhat unstable classic Mac OS), I feel that we have experienced a decline in the user experience.
I personally believe that Windows 2000 was the best version of Windows despite its security issues. Windows 10 is technically better, especially with its Windows Subsystem for Linux layer, but unfortunately Windows 10 doesn't support Classic Mode like earlier versions of Windows, and I find Windows 10's telemetry, advertising, notifications, and mandatory updates highly annoying. Windows would be a great OS if it weren't for its annoyances, which is why I hope that one day ReactOS catches up with Windows 10 in terms of compatibility.
I personally love macOS, but its EULA ties it to Apple hardware, which I've become increasingly disappointed with. And, quite frankly, I have a soft spot for the simplicity and consistency of the classic Mac OS, even if its architecture needed a complete re-haul.
As for desktop Linux, while it definitely has all of the components necessary for a modern OS, it lacks the fit-and-finish that macOS has. Part of it is due to the very nature of the development of desktop Linux. Unlike Windows and macOS where Microsoft and Apple, respectively, have control of the entire stack from the kernel all the way to bundled applications like WordPad, Edge, and Safari, in desktop Linux each component is part of a completely different project that is made by different developer teams who have very different goals, which are often not aligned with a larger vision of providing a coherent desktop experience. Now, one can find greater consistency by sticking to applications that follow the GNOME and KDE user guidelines. However, many applications don't follow either one of these guidelines. I find that Linux distributions have the uphill battle of trying to create a consistent, coherent environment out of a collection of discrete, disparate parts. The result is a system that may very well be just as full-featured as Windows and macOS, but it feels more like a collection of parts rather than one coherent system, which becomes apparent whenever something breaks.
I would love to use a desktop operating system that provides coherency and consistency while also allowing the user to have full control over his or her environment. I also want to use a desktop OS that is also unabashedly and unashamedly a desktop OS and not one that tries to integrate a user experience that is more suited to mobile devices rather than desktop computers.
Unfortunately operating systems are very capital-intensive to build. This blog post (http://mmcthrow-musings.blogspot.com/2019/06/my-2019-mac-pro...) contains more information about what it would take to build the type of system that I would love to migrate to.