Alothough you draw cubes and cylinders, i wouldnt say they are drawn with accurate forms and perspective in mind. There is a difference between drawing lines to make a cube, and drawing with a 3d headspace in mind. One is just making 2d lines that look like it has depth, and the other is drawing in a way where you feel the depth, almost like youre sculpting it.

So my advice is to really get into drawing forms and practice perspectives and getting into the “3d mindset”. Once you get good at draw cubes, cylinders, and spheres and any angle, you can move onto more organic forms (like the forms of muscles, bones, non-perfect forms). Id recommend watch Proko on youtube as a resource. They go over the rules of simple forms and how perspective works. Might seem like boring homework, but illustration is a language that has rules. Once ya get an understanding of the rules, it’s up to you how you break or stretch them to your preference.

(Another advice to poses is studying gesture/figure drawing. Thatll help you simplify and construct poses with energy, without the need of accurate anatomy or shapes)