It's unusable even with the "user-friendly" distros like Mint and Ubuntu. Starting with the fact that Mint and Ubuntu don't even agree on what window system to use.
I don't understand. First, how is that a problem? Second, why is it the default expectation that different operating systems will have the same set of flaws?
Fragmentation makes compatibility and help-finding more difficult. And newbies do get the expectation that the mainstream options aren't all that different, cause that's what everyone tells them.
You kind of moved the goalpost there. That's different from them being unusable. Windows and OSX are different from each other too, are they unusable as well?
I didn't say that fragmentation is the only thing that makes them unusable, it's just one of many. Yeah it is a big thing though.
People do have difficulty switching between Mac and Windows, but each has critical mass so it's still easy to get help with the finer details. And unrelated to fragmentation, anyone tech literate won't have nearly as many showstopping issues to ask about there in the first place.
The big problem isn't friendliness, it's that you don't buy a laptop with it installed. Most people are not realistically going to install a different operating system, they're going to use the one the laptop comes with.
I am quite sympathetic towards Tuxedo, and am considering to replace my work laptop (a 6yr old MBP) with one of those when it stops working, but those are Apple and gaming laptop prices, not mass market prices.