That's not strictly true. The resources were (and are) there, but they have been pointlessly squandered.
KDE3 and GNOME2 were great desktop environments. I would argue that KDE3 was the pinnacle of all desktop environments to date. Polished and usable, it was absolutely fantastic to use. Great UI, great design, and having KParts embedded in Konqueror made it really flexible and extensible. I used it for many years, and took advantage of its functionality unlike any other DE. I also used GNOME since the 0.9x days, and it also became very polished, if not less sophisticated overall. GNOME2 was definitely its peak.
What happened though was CADT. All the effort expended to build up these DEs was carelessly torn down to be rebuilt in an inferior form. Today, both of the major DEs seem to be busy aping mobile UIs instead of creating desktop UIs. GNOME/GTK have scrollbars with zero buttons and sized about 4px wide; totally unusable on a 4K display. They even broke the old paging and panning behaviours, which were excellent. They have almost completely lost their focus on the desktop, and with it, the developer base which formed the long tail of contributors.
Part of the problem is that the upcoming generation of developers have predominantly known mobile UIs; they haven't fully experienced or understood the sheer breadth and depth of rich desktop UIs. The other is that with the switch to mobile devices, there simply isn't the money in desktop UIs nowadays. While this isn't strictly a bad thing, in practice it's the loss of diverse commercial inputs which has driven GNOME off the rails and made it an insular echo chamber of bad ideas.
That was the only Linux pain point for me, having to manually toggle out of multi-screen mode after unplugging an HDMI cable. Obviously, that was some kind of kernel thing and not an XFCE-specific bug (I think?), but even the native XFCE tooling has improved in the last few years, despite the lack of a newsworthy major version release.
Fedora has been my daily driver for 8 years now. It keeps getting better. The last flaky distribution, for me, was Fedora 19, released in the summer of 2013! (Here, flaky is described as "difficult to get working the way I wanted" and "occasionally would do something weird and force me to reboot it to fix the problem")
That's funny because it's exactly the way I feel about macOS where they obviously design things based on the way things look and sell over how usable they are. This is actually part of Apple's DNA as we've read in the past: The only reason they stuck with the Dock was because of how well it marketed. You can read about it from the guy who developed Apple's first HIG - https://www.asktog.com/columns/044top10docksucks.html
Meanwhile my preferred Linux DE (XFCE) gives me perfectly tasteful design and coherent usability. Instead of having things look or work the way Apple wants, I am able to do things the way I want to, which means that things fit into my opinion of what is tasteful or usable. It's a ton of little things you know? Like being able to quit an app with a single gesture (a middle click on its pane icon, similar to how you close a tab in your browser) - built into XFCE and not even available in macOS unless you're Apple and you have some access to their private API.
That's because most Linux desktop environments take after Windows, which has by far a better system of usability than macOS. To point out just one small thing: In macOS the keyboard shortcuts are an insane jumble of incoherence with no pattern which is why you simply cannot navigate the entirety of macOS with just the keyboard, something that I can do all day long on Windows and Linux.
If you think you can, I'll challenge you: Open the About this mac dialog, then switch to another program. Now try to switch back to that window with just your keyboard, without using one of your special usability-fixing programs that you have to install to fix such things on your Mac, like Witch.
That said, I consider XFCE great and all bugs I encountered while using it were minor.
Many years ago people would complain about even getting things installed, have stories about driver problems, missing software, incompatibilities. If today's strongest criticism is "the clock widget sometimes does not rotate automatically", I think that is a great endorsement.
But, it's the overall experience that sucks in Windows (and most linuxes imho).
Regardless your last point is why I stick with macOS. I don’t really care that much about the laptop aesthetic.