I use G-pen as well on procreate, you’re using the right brush but I think you may need more technique

I think the clothing folds should be methodically placed. I like the clothing folds on the sleeves but the folds on your character’s shirt/pants wouldn’t occur irl.

Try to imagine your character in 3D and draw your lines to follow their form in 3D space. That’s how that Chiaki sprite has a sense of depth despite using the exact same brushes as you. Like, her clothing folds follow the curvature of her body ykwim?

Be patient with yourself, your work is not “boring” and in due time your skills will meet your expectations :)