Not as True as You Think
If you can say "more than 90% of the open source software is dead, unfinished, low on the development timeline or even just not very good," then you can say it about proprietary software as well. That doesn't really mean anything. There is a significant core of good, quality open source software available. I know there is because I use it all the time.
Usually, the issues with software availability with a Linux system are about either software to manage or connect with specific devices or services (e.g., I use a Virtualbox Windows XP install to manage my hiking GPS), or else about a specific software that's very popular (like AutoCAD or Photoshop).
Major software vendors can port Linux versions if they want to. That's what install scripts, static dependencies, and the /opt directory are for. It's no more difficult to make a scripted install for Linux than it is for Windows, and that was the major way Windows software was distributed for a long time (a lot of it still is distributed that way). I used to run games from Loki on whatever Linux distribution I wanted, and it wasn't a problem (making sure I had Nvidia drivers available was a much bigger deal at the time).
People have this odd idea that the issues with using an open source package for one distribution on another somehow relate to proprietary software. They generally don't. Open source packages expect certain dependencies and expect to communicate with the package database. Closed source software installs include their own dependencies, except for possibly listing some more general requirements like accelerated OpenGL support, and they don't care what else is on your system.
