Is “Middleware” the name of a graphics library? Or are you talking in general, saying that using an intermediate library is better than using the platform’s API?

An intermediate library like Ogre3D, or more full blown engines like Unreal/Unity/Open3D and so forth.

All of them use the platform's API to take advantage of all features, while providing a more high level of 3D programming concepts.

I understood this to mean things like Unity

That’s a bit of an over generalization. Many studios do not, and many more have not always used middle ware to deal with multiple APIs.

Sure, many studios also only do console exclusives, while other studios specialize in porting services, for example.