The vast majority of Windows applications uses probably 1% of the API. That's why you can play a lot of games or run a lot of different apps and they mostly seem to work and only usually the obscure features like the help section or something might not work correctly.

In this case it looks like Adobe was doing a bunch of stuff related to Internet explorer that was critical to even having the basic functionality of their installer or launchers working.

Oftentimes if you take a program that is not running correctly or at all you can look at the log output and see a large stream of unsupported or partially supported API calls.