You claim not to be obtuse yet you still haven't responded to the point that's now been presented in multiple ways.

If I use unity did I write my own game? What about a framework such as bgfx? Or am I required to write my own calls to standardized 3D APIs?

The important detail isn't what was and wasn't pre-made (there will pretty much always be something that was pre-made) but rather the list of contributions by the individual. If I use tomato sauce from a can and a frozen crust you might or might not be impressed by the pizza that I "made" depending on how far I went beyond that starting point.