For me I think it is a little different. There are tons of beginner material and even quiet a few advanced materials, I find the middle (or intermediate) materials lacking. For example, with rendering. Tons of great content with indepth explanations of how to draw a triangle. You can also find lots of good tutorials about advanced procedural generate techniques, but they (correctly) assume a lot of knowledge that is above the simple task of rendering a triangle. There isn't a lot of content to help you get from rendering a triangle to the knowledge you need for some advanced rendering techniques.