They have so many patents on hardware that they could licence the system and clones would still not being able for example to have Apple like touchpad, touchbar screen, MagSafe or even continuity (they could block it for licensed hardware). They will not do that because they realise that they fantastic, proprietary features means nothing to average pro user. Stuff like that is nice to have but more important than that is to be able to run all needed applications reliably. Currently on Macs are only iOS devs and people that hate Windows. That second group could go to linux only if there would be Adobe Suit available on it.
you're a bit aggressive : I use it daily and it definitely works (but I work with it : no games, almost no 3D, just PyCharm, git, LibreOffice, firefox, irssi and claws mail on openbox WM; scanning/printing a document from time to time nothing fancy)
Latest problem I had were with the printer driver (Brother HL-1110 which doesn't seem to know that this printer has much less memory than advertised)
I think that's the key to Linux on the Desktop. It generally ranges from very limited to terrible for your average end user. Your video professional might fare slightly better, but realistically is only going to use Linux if they're working at a company that's invested in Linux for their video production stack.
Where the Linux desktop is truly unparalleled is for a developer. As a developer I'm comfortable enough with the technical details to handle the quirks (like doing things from the command line), and the strengths of Linux truly shine (again, the commandline, as well as choices in DE, software, etc). One great example is Arch. On Arch I can install any developer tool directly from the command line with very little effort. Anywhere else and you have to click through endless menus.
