You currently can't develop a Linux desktop application, that will run unmodified on a Linux desktop five years from now. A successful application ecosystem like the Android one needs a stable API and stable interfaces. Otherwise you're just reimplementing the same trivial stuff over and over again (How many terminal emulators and Finder clones are there?)

Stable interfaces is something the major Linux players don't want. On the opposite kernel developers implement a DRM to deliberately break third party drivers, because they're just not affected by this on their nifty MacBooks.

The Linux desktop fails, because the people in charge want it to fail. Full stop.