I mean theres a few things. One youre definitely a beginner. The people youre looking at are more likely intermediate or advanced, so theyve had way more experience than you. Second youre using a ballpoint pen for lineart. They are notorious for not being consistent. You also are leaving things in the sketch phane which is not a clean finish
#Characters
drifting perch
In the end it all comes down to practicing and doing exercises to specifically work on having clean lineart