MacOS is built on BSD, which is like Linux but more arcane (sort of). (Edit: also the Android kernel is a Linux kernel). If you don't find yourself using the shell in MacOS (or Android), it's because they've done the work to make it unnecessary. The command line is still there, and can still be used to fix (or cause) problems.

The companies developing your audio software release it for Windows or Mac because that's what the users are running. If the majority of their users were running Linux, they would be releasing Linux binaries.

As for being more reliable... it depends on your use case. Around 79% of all publicly accessible servers on the internet run something Unix-like, with about 38% of the total being Linux. Windows is used for about 21%. In my sysadmin work, I use Windows when it's mandated by the software (again, because the developers chose to release for Windows only, not because the software is fundamentally tied to it), and Linux everywhere else. Reliability is a big part of that decision.