Every time I install Linux there is something that doesn't work. As recently as last year it took me days to get the Wifi working because of driver problems. I still haven't got Bluetooth to work right on my current workstation. Similarly the USB file transfer UI is broken because the buffer size is too large and it's not been accounted for in the transfer completion calculation. It's a million things and pretty basic and essential ones.
And it's impossible to debug, you have to spend 10 hours typing obscure commands because the Linux voodoo-priests have never heard of buttons and GUIs.
It used to be that Windows worked for every standard small functionality. And on the rare occasions when you had a problem you would immediately know what part of the control panel or the registry to go to and fix it yourself. Occasionally you had to google and people would give you simple instructions to follow. That was before Microsoft ruined it, but my point is there was a clear difference between Linux and Windows and the best Linux distro did not come close to the level of UX that Windows did.
It's not a fair comparison because Linux is so fragmented but to me it remains that the Linux desktop experience is broken in some way for many people who use it.