That wasn't even the gripe. They have disliked the last few major revisions of macOS. I think that's a good enough reason to consider a switch.
I do feel some Linux or perhaps a BSD system with a GUI like WindowMaker might feel like an improvement at this point.
It’s something I will probably try in the coming year.
I'd like to have a system that is 'less secure' in which I feel I have more control over my system.
Also it seems Apple is moving apps included in macOS to be more in line with iOS, which is not really something I like to see. It will likely dumb down app functionality.
I used OS X exclusively from 2008 onward, and I switched fully to linux late last year. I managed to make the switch tolerable by learning and falling in love with tiling window managers and minimal desktop environments that are available on linux. I could never stand 'traditional' desktop environments on linux, they always felt so clunky. With Sway (or i3 on my desktop), the operating system just disappears out of sight. All I see is what I want. A little bar with information and system status, a browser window, a bloated text messaging program or two, and heaps of terminals. Really fast, too, unlike macOS.