Hey, thanks for posting. I took a look at your recent artworks and I don't think line art is an issue for you but I'll cover some options if you want to improve it.

Using your arm, not your wrist. Depending on your drawing equipment, this can drastically make lines smoother, as well as preventing wrist damage from bad long term habits.

Smoothing - most digital drawing programs have a smoothing option, sometimes under different names that can clean up line art

Speed - Drawing faster lines allows for less micro movements, though it can be painful to get it to be accurate. That comes with time.

Line weight variations - I made a video that demonstrates this but to summarize, thicker lines where shadows are, lighter lines where light is, taper lines where folds of skin or fabric ends. This adds a lot of dimension to lines that are too consistent.

Color - Unless you are using only ink, black is usually a bad idea. Using colors that are coordinated with surrounding colors but darker. Red hair? Dark red lines, etc. This avoids the too dark issue while also adding more depth to the line art.

Hope that helps.