The code is given to you with a high-level explanation and that's it. It's like showing a person an airplane and then explaining the physics that make it fly. It doesn't matter if the learner understand the physics, they'll still crash.
A tutorial for a high-level graphics task won't be written for absolute beginners. That's absolutely natural and common, in all areas, not just programming.
The standard process of learning ANYTHING consists of steps or lessons or levels etc.
Tutorials usually cover a specific problem. There are tutorials how to create a Direct3D device (plenty of). There are tutorials how to render a triangle (again, plenty of). There are even tutorials covering both of those (as creating a device alone isn't much attractive, so most beginners tutorials include also some rendering). But you cannot expect these basic tasks to be fully explained in every tutorial. People who are interested in HDR rendering would be bored with chapters 1 to 20 (out of 25), because they know how to do it, they are interested only in HRD.
Yes, such a tutorial could exist, everyone can simply skip to the chapter he's interested in, no harm done. But who would want to WRITE such a tutorial? Who would want to explain all the basic stuff again and again and again? Who would make 50 pages long tutorials just to say on pages 49-50 how to filter shadow edges?
What you really need is a SET of tutorials, or better a book for beginners - such books are great, as you progress in reading, you progress in your skill.
I can use your analogy with airplane. Try to think about it, if we take it into extreme, what you really want from the tutorials is something like specialized instructions "emergency landing with landing gear failure" containing also the whole description how does a plane work, how to start a plane, how to take off, how to fly etc. That's not a tutorial, that's a full manual.
Or, maybe a better example -
do you think that it's wrong when a math schoolbook titled "differential equations" expects the readers to know basics and just uses terms like "multiply two numbers" without further explaining HOW?