Earlier quoted context omitted.
There is definitely an element of nostalgia. However, a lot of earlier desktop OS GUIs do seem to be more internally consistent and with more emphasis on usability than the current crop. I think part of the issue is that things that might make sense on a phone have bled into desktop OSes, where they make a lot less sense.
I don't mean this in a dismissive way but based on your profile I'd say you're > 25. I'm curious about the perspective of someone who didn't grow up with the those os's
Also, there's simply the reminiscing back to the era when these were out. When they were NEW, and revolutionary.
All things that cannot be conveyed from a static screenshot.
Consider NeXTStep. Something you cannot see from these images are that when you moved a window on NS, the entire window moved. Not a frame, the entire thing. This was not normal in the day. Or that NS used Display PostScript. "Not only are they moving the entire window, they're using DPS to do it!" PostScript was powerful, and expensive, and for printers. Yet, here it was.
Or how fast BeOS was, and its cool filesystem, and other aspects.
It's certainly an interesting question to ask folks that have opinions simply on the cosmetics of the various images that we see here, but appreciate that for the folks that "were there", at least for me, I'm not just remembering what it looked like, it's much more than that.
I will never forget when the Mac first came out, my friend and I went to see one at a computer store. And my friend just sat there, mouth agape, moving the mouse back and forth across the menubar, seeing them popup and popdown as it moved, and just going "Woooowwww".