Do what author / illustrator Kamiya Yu (No Game No Life) did and just trace everything.
People underestimate how much commerical artists and musicians cheat to make everything perfect.
Also, perhaps you're not going into each drawing with good parameters. To take an analogy from an area I know well, game dev, people tend to make one "rambling" big game and put everything into it, but they don't have a strong sense of what they wanted to achieve and how much work that would be. So they end up with one big non-playable game that they never feel is "finished" enough to show anyone. This is very common.
One good bit of advice I've heard is to budget time, then plan and deliver a "game" in that amount of time (e.g. 7 days). And it has to be "finished" even if it's simple. If you don't finish, then you had planning problems. Write a post mortem explaining what went wrong then plan a new project. If the first plan was too ambitious, scale it down until you know what is achievable for you in 7 days. Do enough of these and the planning phase will be more and more accurate, while you build up a toolbox of technique, and you can start to plan bigger things as well, but with confidence you can finish them by a set date.
You could apply something similar to drawing. It's possible that your drawing suffers from a similar lack of planning. If you don't know exactly what you can achieve in a set amount of time, and you're only trying to make it "as best as possible" then perhaps you're not planning well enough or spending too long on some stages trying to get things "perfect" when you should just move on and finish the piece then just try another one.
e,g. know you're going to make a piece, it's going to take some set amount of time, and you pre-plan what you want to achieve in that time. e.g. you say "I'm going to draw a cat, and it's going to take 5 minutes". Work out the plan of how you're going to draw the cat (whether it's lines or a pencil-sketch-then-ink process etc) in terms of which stage follows which other stage. Then, start a timer, and execute that plan. don't rush the work, do things as properly as you feel they should be, even if it's slow. If you didn't finish adequately or in time, then look at which stages went wrong, what was too complex, what could be streamlined. Then plan a new drawing (possibly simpler) until you know what you are able to produce exactly in 5 minutes.