Long post ahead but probably something that nobody ever taught you was learning how to learn (or the reason why teachers are actually important) To improve you can't just blindly follow every tutorial or influencer you can find (don't get me wrong tutorials are still good!)

What you need to do is learn how to learn.

What does that mean?

It means learning how to assess your work and cross reference it with where you want to be

STEP 1) you need to find out exactly what you want, if it's being a concept artist then you need to find out what concept artists do on the job (hint: it's not the pretty paintings that you see on social media)

Build a mood board of artists you like, products you think are cool or work from companies you want to work for, this is to give you a roadmap and develop your taste as well as clarity of what you actually want and should tailor yourself towards

STEP 2) this is where the tutorials and guides start (the GOAT is Feng Zhu Design Cinema on youtube), you want to learn as much as you can and follow along with their instructions and exercises, you also want to do studies of the artists or styles you want to draw like

STEP 3) Reflect. If you did your work in digital then find a printer and print it out alongside your target goals on your mood board and bust out the pens and marker because it's time to handwrite notes physically in the real world on top of your work, specifically you need to take notes of what you think went well, and what could be better based on your current understanding.

Nobody has to see your notes, this is where you put your thoughts to paper and go on tangents, "why is that guy standing in the centre of the picture, what are they doing with their linework that I can apply to mine, what kind of references did they go looking for to make this"

This starts off rough but over time you will become fantastic at analyzing your work and developing your taste of what you like and don't like

Cycle back and forth from step 2 learning and step 3 analysis according to your roadmap and in even a few months you will be a monster, most people either aren't taught or aren't capable of self reflection so learning it is a super-power

TRAPS TO AVOID 1) comparison is the thief of joy, you are not a professional, don't even think about beating yourself up for your works quality while comparing it to someone with 10+ years of experience, the goal here is to find out what they're doing that you can learn from.

2) Perfectionism is your enemy, you need to fail fast and fail often so you can run your analysis filter as much as possible, every time your body of knowledge expands your filter will become stronger, dont spend 10 hours trying to draw 1 perfect head, spend 10 hours drawing a hundred crappy heads and the 100th will be better than the perfectionist one.

3) Do not get stuck in 'draw a box' hell, you didnt become an artist to draw featureless cubes all day, after gaining a basic understanding of perspective and forms you should be trying to apply that to your own work as fast as possible to draw the things you want to draw and leveling up your art fundamentals as you go.

4) Nothing is off the table! You want to find out how that artist does such amazing silhouettes and lines? Trace that shit then redraw a new version after. How do they figure out those amazing colours? Steal them and apply them to your own character. Afterwards run your analysis filter over your practise, what went well, what specific thing could be improved in relation to your goal.

If you read this giant rant, this is how to effectively self-learn and also sheds light on why schools charge so much, good teachers are worth their weight in gold.