ChromeOS is a far better "Grandma" distribution than Windows or MacOS. Linux is simultaneously both the most Grandma friendly and least Grandma friendly, including every point in between.
You need to compare apples to apples, aka pre-installed vendor supported operating systems. If you're comparing installing an unsupported OS on unsupported hardware, Linux is far superior. Try installing MacOS on a Windows computer or Windows on a Mac if you're truly masochistic.
Are you saying windows and macos do not have any bugs? I have news for you.
Also wevare talking here about archlinux + hyperland compositor, not the typical Fedora, Mint or Ubunti/Zorin distro. Tinkerer's gonna tinker while the other users just use their computer regardless of the OS.
Linux isn't a single OS. It's hundreds of different and weird combinations.
There are Linux distributions that are better than Windows or iOS for grandma to use as well as distributions where you need to be an expert to do anything.
It doesn't matter, your options are either X11 or a Wayland-based compositor, both of them come with their respective headaches that a regular user has NO IDEA how to fix.
How can anybody seriously argue Linux is an OS ready for ordinary users when you have to do crap like this? Complete delusion.