I've been thinking a little bit of the different categories that make up "drawing skill", because it isn't as simple as it seems. When starting out in art, just doing a bunch of drawings will improve your skill a great degree. But at a later point in development, it becomes a lot harder to figure out what to work on in order to improve.
I forgot which episode of the Draftsmen podcast it was, but one of the co-hosts (Marshall Vandruff) talked about something that he had heard from a friend about the three skills that are needed to create good art pieces. And after hearing about it, it helped a lot with knowing what to work on next to improve my work further.
The first category is technique, which is basically how to handle your tools. Holding the pen properly, proper technique for making clean and confident strokes, etc. This category becomes blatantly distinct from the other skills when you try to draw with your non-dominant hand.
I found that if I drew with my non-dominant hand, I could still somewhat draw things properly. The only real difference being that my lines are going to be more clumsy and unconfident, because I haven't properly ingrained the muscle memory needed to make clean strokes with my non-dominant hand. Having good technique doesn't necessarily mean that you'll be good at the other skills. It only covers the handling of said tools, but there's going to be a little bit of overlap of course.
Technique also covers skills specific to certain mediums. There are only techniques applicable to traditional painting mediums (oils, acrylics, watercolour, etc.), such as wet-on-wet, wet-on-dry, and things like colour mixing. But most technique does transfer over somewhat to other mediums.
The next category is draftsmanship, which is a term that gets thrown around so much nowadays to the point where it lost its meaning, but in this case it was defined to be the manipulation of form. Being able to deconstruct complex objects into simpler volumes, turning things in perspective, applying proper anatomy, proportion, and things like that. It allows the artist to construct things (whether with reference or from memory) in an accurate manner.
I'm not sure whether observation falls into this category, but it really should. A certain level of observation is needed before you can even analyze an object and deconstruct it, but the deconstruction and construction part needs to be trained on its own.
A pattern which I've seen often is that the artists who are really good at drawing from memory are also really good at observation. However, it's not always the case that being good at observation means that the artist is good at drawing from memory. Proko said himself in one of his livestreams that he spent basically 10 years working on observation and he became too comfortable with it to the point where he had to start training his visual memory exclusively just to be able to draw things from imagination. So it's best to start training to draw from memory when your observational skills are at a decent level.
And the last category is composition: how the artist puts all of these forms together to create an art piece that conveys their message, or tells a story. It's the last step that combines everything together, and it's where all of the decision making happens: which colours to pick, what the focal point of the piece is, how characters are going to interact with each other and the environment, etc.
I like how the categories are ordered in some way: technique → draftsmanship → composition. It's ordered from a micro view of drawing to the macro view: technique covers how lines and strokes are made, draftsmanship is the application of said lines and strokes to create form, and composition is how to place the forms to create an art piece. There's a natural order to it.
It's important to note however that one doesn't have to "master" one category before moving on to the next, as all of them reinforce each other in some way. But there is a reason why certain beginner art courses (ex. Drawabox) are structured in this order, and that's because one category relies on the other. It's hard to make a good composition if the skills behind it are weak. This is probably why composition is more of an advanced topic that is not typically taught to beginners, among other things.
Some genres of art are only really composed of two out of the three categories. An example would be abstract art using mainly technique and composition, with an emphasis on brush strokes and colour to evoke emotion. Another example would be schematic drawings using primarily technique and draftsmanship, prioritizing accuracy. But a lot of artists use all three in some way, with some being better at certain categories than others.
Now this brings up the question: what's the point of splitting drawing skill into three categories? Well, as I found out for myself, it makes it so much easier to diagnose what my currect weaknesses are and thus lets me know what to work on next.
As an example, if I were to keep working on technique despite it being my strength, then my skill set would be quite unbalanced. After a certain point technique alone will stop improving my art pieces because my draftsmanship and composition are the limiting factors that are hindering my work. An unbalanced skill set may be the reason why some artists have stagnated in development.
These three facets of drawing skill are more of a diagnostic tool to figure out where an artist is in their development, and what they need to work on. There are probably a lot more categories that make up "drawing skill", but a lot of them fall into these three categories.
Hopefully it helps to know where to invest your time to improve at a faster pace, though of course art is not only about improvement; having fun with the process is something that some artists (including myself) can forget when working on their skill.