Why is it so difficult for third parties to produce good software for OS X?

I use two pieces of hardware from different companies for my music that connect to the iMac via USB. With the OS X upgrade to Catalina, both of them stopped working and both companies said that because of changes in the OS X, their software would need to be completely rewritten which both of them have declined to do and advised me to switch to windows for which they had working software. Prior to the OS X upgrade one of the companies programs were so buggy that it was 50-50 whether or not it would run each time I wanted to use it.

I recently tried the 3-Dconnexion spacemouse for my CAD. The first attempt at installing the software failed. With their tech-support I finally got it installed, but it simply wouldn't work as advertised. I then tried the Kensington expert trackball. The installation of their KensingtonWorks software also failed. When I finally got it installed my Mac slowed to a spinning beachball for minutes at a time. Totally unusable.

The Adobe creative cloud frequently warns me that creative cloud is missing or damaged and asked me to download and install a new copy.... again, and again.

My CAD program is Autodesk Revit which is becoming the de facto standard in the architecture and construction industry. Autodesk refuses to create a version for OS X so we are stuck with 1 foot in the world of windows, which in my case is a windows virtual machine on parallels.

So I wonder with such beautiful Apple hardware and software, why is it so difficult for third parties to produce good software for OS X?