Linux biggest problem is that they (Distro makers) were never willing to raise some serious money and actually try.
Yeah, it's a little hard to "sell" something for free and compete with the $$ marketing campaigns of major closed-source companies. Want to tell us about how easy it is for you to raise some "serious money"? I mean, whenever you decide you're willing to raise it.
Flat, high contrast UI is what's "in," get with it.
I'll stop here as I could list about 10 serious issues such as these.
Um, yeah. If you think adopting the latest gee-whiz, touch screen-obsessed, desktop-crippling, dumbed-down UI on a desktop OS is a "serious" issue, I'm pretty sure I don't care to hear about your other 8 "serious" issues.
Once in a rare while I install and open some old app that's no longer in development and is stuck with some old turn-of-the-century GTK/GTK2 UI. So ugly! Yes, things were crappy in 2000. You couldn't even install a popular Linux distro and expect it to "just work". Hard to imagine that today!
The only trouble I have with Linux (I currently use Ubuntu) is a recent regression on my MacBook Pro--used to work perfectly, and still does on the Mac Mini I'm using this very moment. But even with some ACPI issues on the laptop I'm happy I don't have to use OSX on it. But sorry, I digress. I was talking about actual functional issues, nothing as "serious" as the latest high-contrast, flat UI fashion.
As for the UI... yes, things sure have improved a lot in the UI/UX world in the past 17 years, except in the MS world which seems seems to have been devolving for a few years at least, and I commend Linux distros not keeping up with touch-obsessed disgraces like the Aero/Metro UI that looks like a card game or something.