It's easy to talk past each other when discussing which techniques to prioritize. Drawing forms in perspective is a large hurdle, and it is important if you wa

It's easy to talk past each other when discussing which techniques to prioritize. Drawing forms in perspective is a large hurdle, and it is important if you want to work quickly on a variety of projects with little reference(a common need in professional illustration) but also not the defining thing of "drawing". The huge number of artists that define themselves in a completely flat style should signal as much. I found it was more important in my studies to prioritize proportion. Proportion rules over and interacts with everything else - it is unavoidable, and there are many proportioning tricks and strategies out there. Drawing on the Right Side of the Brain is fine at guiding this basic principle. The other things can be done with a bit of reference and specific techniques: If you understand the proportions correctly in an orthographic side, front and top view, you can already create character turnarounds: just rotate the top view in 2D and then draw guidelines downwards, and you have the horizontal location of everything after rotation, which can subsequently be matched with the vertical from front and side. It is a major labor to do this because you will most likely not have perfect proportions in your original views if you drew them from scratch, but the process itself is intuitive and accurate, and involves no cubes or cones. Form in perspective is likewise mostly reducible to knowing the location of the horizon line and then informally distorting proportions according to the rule: "above horizon=looking up, below horizon=looking down". And then doing studies of the perpendicular cross-section to internalize the detailed form of real objects. Again, cubes and cones are not a priority. They are a method of simplifying, which helps when you aim towards arbitrary constructions from imagination, but the drawing assignments I've undertaken are achieved with most accuracy by starting from either using a maximum detail reference image to set proportions, or first working in orthographic views to simplify understanding. The emphasis on primitives is primarily a yesteryear's art education phenomenon, because it was much, much harder to get accurate references then. Artists were known for possessing giant stacks of source material. We're in a world defined by digital processes, and the stacks are disappearing accordingly. You can easily tell the computer to make an accurate cube and then trace over that, and if you need more details you snap a quick photo on your camera. You can build up exactly the reference you need via photobashing. The process is a giant shortcut that doesn't give the same results, but when pushed hard to be stylized, it still leads back to the traditional skills of observation, and eventually to drawing cubes.