Very important sidenote: I did not draw that, I found an amazing artist to commission. If I'd have only 1% of that skill I'd be a better drawer than I am today.
Aimless practice is good for creativity, not for skill. There is a plethora of studies that show that deliberate practice is what you need to do to actually get better. You need to define what's good and then do what Cal Newport calls "stretch and destroy": stretch your abilities to an uncomfortable level, and embrace honest feedback even if it destroys what you think is good. You should judge tutors by their ability to help in those two regards, if you'd ask me.