Only back in the day part of the idea around "Linux for the Desktop" was that everybody would use the "better" FOSS programs, and not wait for MS/Adobe/Autodesk/Avid/etc.
But, as you note, this hasn't happened, and "even if you fix GIMP's UX issues, it's still not Photoshop or Lightroom".
>But that's not what being ready for the desktop is about. That's not what a desktop is for most people, either.
Well, pragmatically the desktop is a Windows machine, which just works, doesn't require them to think long and hard about which cpu/memory/laptop/peripherals/etc to buy, has drivers for all of their devices, has all kinds of apps they might use (beyond email and web), and so on.
That wasn't really like I and many others envisioned, no. Free software have other benefits that make them "better", not merely technical issues.
It's not a technical problem because people like my mom can learn to use GIMP (note: people who use photo editing software are "pros" of a kind, anyway; "regular" users don't know how to edit photos, either) or Krita or whatever. But even if you fix GIMP's UX issues, it's still not Photoshop or Lightroom, so the problem remains: there's no Adobe software for Linux.
But that's not what being ready for the desktop is about. That's not what a desktop is for most people, either. All in my opinion, of course.
PS: if Lightroom magically makes it to Linux (hypothetical thought experiment), but then it's Overwatch or some other high profile AAA game that doesn't run natively, is it still a problem of the Linux desktop?