How can I learn the technical and theoretical aspects of blender and 3D in general?

Tutorials (and even paid courses!) generally don't explain the hows and the whys of what they are showcasing, I feel like the general expectation is that you should just follow along, sometimes resulting in "draw the rest of the owl" situations.

I'm interested in knowing the inner workings of 3d in a general sense, the skills and resources necessary to find solutions by myself and create my own plugins and more generally how to think like a technically capable artist.

Is it just trial and error or there's some sort of general theory book or course that I can look for?