If I had to guess I would say it’s because this drawing is not conventionally cute.
The reason why that is it’s because both of the characters have a man’s anatomy while supposedly being cute and wearing dresses.
Since most people prefer designs that have complementary elements this clashes with that.
Like for example, if it’s suppose to be cute it should have a feminine angle. Soft rounded corners, less broad shoulders, stuff like that.
The shading is also somewhat unremarkable, some shadows are barely visible and the contrast is low.
It’s completely fine tho, Don’t despair original artist.
I also have my fair share of less than perfect drawings.
Just study human anatomy and see what people respond positively to and you will get up votes.