This design seems to cement the trend at Apple to position their products as consumer appliances, not platforms useful for development.
The problem is, there's nothing else out there. Everything is going to shit in one way or another. Windows is now a disaster, Linux was always a disaster in terms of user experience and isn't improving.
Mac OS was the last bastion of somewhat good, thoughtful design, user experience and attention to detail and now they've gone to shit too.
Curious: what have you tried? People who use "Linux" as a catch-all in terms of UX usually have only tried a single distribution with a single desktop environment.
- multi-language support requires a lot of work to get to the same point as macos.
In particular I use third party shortcut mappers to get language switching on left and right command keys (mimicking the JIS keyboards, but with an english international layout). That looks like something I’d have to give up on code myself.
- printer support is not at the same level.
Using a xerox printer, some options that appear by default on macos where not there on ubuntu. I’m sure there must be drivers somewhere, or I could hunt down more settings. But then my work office two other printers. It would be a PITA to hunt down drivers every time I want to use another printer.
- Hi DPI support is still flagged as experimental, and there’s a bunch of hoops to jump through to get a good setting in multi-monitor mode. Sure it’s doable, but still arcane.
- sleep/wake was weird. It would work most of the time, but randomly kept awake after closing the lid, or not waking up when opening. Not critical, but still not good (I’d ahte to have the battery depleted while traveling)
Overall if I had no choice that would be a fine environment. But as it is now, with all its quirks, I feel macos is still a smoother environment.
Portability is also a fair issue to raise, but it's simply not a problem for me. When I say Linux "on the desktop", I literally mean it: to me a laptop is simply a slightly more portable desktop computer. I sometimes take my work laptop to/from the office, and the battery lasts long enough for that. I'm not worried about longer trips, since I don't use laptops for that. Again, if you do care about this (which is completely fair), I'm aware many Linux distros still have issues with battery life. You certainly can't compete with a Macbook Pro, that's for sure!
I do note that my experience with printers is opposite to yours. Like I said, when trying to connect to an HP wireless printer, Ubuntu autodetected and self-downloaded the necessary drivers; however, it took a lot of patience to get it to work with a Macbook Pro. Today, that I have it configured for my Ubuntu laptop and my wife's Macbook Pro, the Mac will sometimes fail to print (the print job simply stuck in limbo) while my laptop prints reliably. Who knows?
And like I said in another comment, I game (or used to, anyway) a lot with Ubuntu, and many games are even AAA (though they tend to arrive later than on Windows).
So I really have a hard time believing Linux is not "ready for the desktop". It is, and has been for many years now.
edit: one last thing. You mentioned HDPi modes, multimonitor, multilanguage... none of those are for average users. My mom would be comfortable browsing the net, reading mail and watching movies on Ubuntu. She doesn't even know what HDPi is, nor does she want external monitors. (Spoiler: she still uses Windows because she can't learn anything else at this point... I've thought of tricking her by themeing Ubuntu to look like Windows, but that would just be mean).