Linux

There's also XFCE and LXQt, if you want simple, easy-to-use environments.

My elderly, non-techy mum has been using XFCE over a decade across three different distros (Mint, Xubuntu, Zorin) and her experience has been consistent all these years, with no major issues or complaints. If my mum can use Linux just fine - so can anyone else (who don't have any specific/complex hw/sw requirements that is). I don't see how much further intuitive it needs to get.

KDE, Gnome, XFCE, LXQt etc all have their own place and audience. There's no need to have one experience for all - in fact, that would be a huge detriment, because you can never satisfy everyone with a one-size-fits-all approach. Take a look at Windows itself as an example - the abomination that was the Start Menu in Windows 8 (and the lack of the start button) angered so many, to the point that Microsoft had to backtrack some of those design decisions. Then there was the convoluted mess of Metro and Win32 design elements in Win 10, and finally the divisive new taskbar in Win11... you're never going to make everyone happy. And this is where Linux shines - all the different DEs and WMs offer a UX that suits a different audience or requirements. And we should continue to foster and encourage the development of these environments. Linux doesn't need to be like Windows.