Neither male nor female characters in this game look that similar to each other in my opinion.
In fact I think they are all very much different from each other than Barbara/Jean being the exception but they are sisters.
Soon Shenhe and Ganyu will have some similarities but both are students of the same master. So I guess it fits. Their design is different though. You can tell the mood of each character simply by looking at them.
I'm saying that the male characters look boring. Zhongli for example, while being a cool character, looks plain. He's brown/yellow from top to bottom, no/not much play with colours or accessories. Nearly no highlights. His animations are cool but not how he looks.
And many male characters have questionable clothes in general, blame me for being homophobic or something, maybe I am - whatever - but I'm too lazy to find the corrects words for this:
Most of them look gay. It bothers me.
The ones that don't are just as generic as the female versions, but they are male, so there is nothing to like for me.
I mean, look at MC and Kazuha not so unique at all....just different clothing, still different enough but certainly not more than what you say about Shenhe... in fact, a lot less unique actually.