I haven't used Kubuntu for years, but did find while the CLI package manager was pretty solid, the gui one leaved much to be desired. That is definitely a quality of life issue, particularly for less technical issues, but not inherent to Linux. SUSE has long had a "one click install" option, that will automagically add repos and integrates with its package management system, and *is* the sort of thing other vendors could do.[1] It's little different for the end-user than running an installer .exe on Windows or a .pkg on Mac. Personally, I haven't been using the CLI for anything but convenience's sake for quite some time. I read here that they're getting rid of YaST, but there will be other GUI configuration tools to make life easier as well, which makes a lot of that stuff more accessible. And in many ways, the reason I did initially switch distros was that, at least however many years back, Kubuntu specifically had a few things that bugged me going on.[2]
I think that your point regarding "something simple that works" is much more of (and please excuse the pun) a root issue with using Linux daily. There seems to often be a lack of cohesiveness in overall user experience; the KDE folks do a *lot* of work to attempt that, and provide an integrated DE and set of apps, but not quite 100%. In some ways, it's an "uncanny valley" situation. It's most jarring for me when I open up and run any GTK stuff. I don't know how much Windows users would notice, however. My primary machine is a Mac,[3] so I am rather accustomed with, say, the menus of nearly every application following a consistent pattern and other small touches.
[1] Some might have something similar. I'm not much of a distro-hopper and am content to not fuss with things that I don't have to.
[2] Although that PC was my first Linux box, I was already fairly familiar with KDE, having buit/run it with Macports on the G5 that it had replaced.
[3] Where oddly enough, I'm forced to use the command-line for more things, because the GUI can be rather limited.