pretty much what haunter said
since you make more than half with slightly transparent or undefined lines they will always look like unfinished sketches
also it doesn't mean it will take you a long time to finish a single drawing
what it might take is practice but as do all things, and honestly it would be worth it to learn so your sketches turn into finished looking products

with those that you have made look complete i will say i like that i like them and keep up the work or something positive go marrez hero