If the issue is the OS vendor having too much say in what hardware you can use, it's hard to understand what the opportunity is for Apple.

Apple has never really tried to compete for the corporate desktop. It’s too low margin for them.

This. Google and Microsoft are the two juggernauts in this arena, Apple products live on the periphery of the corporate cloud ecosystem.

Based on the corporate IT emails I receive from time to time, it also sounds like Apple enterprise management controls are weak to non-existent. A few times a year, there is a blast sent out to not upgrade your corporate iphone/mac because of some incompatibility. In the Windows world, IT would just hold back the patch without requiring N users to do the right thing.

This is true. Anyone who needs to manage Apple devices in a corporate IT setting is probably using Jamf.

for *BSD and illumos too