What makes a member the visual?

ETA: I’m new to kpop so forgive me lol

To my American eyes, some of the visuals aren’t the most conventionally attractive in the group, but of course they’re all stunning. For instance, I think soyeon in I-dle is so breathtaking but she’s not the visual unless I’m mistaken. I guess my question is what are the Korean beauty standards in the industry that make that determination, and why do the fans so often only praise non-visuals’ appearances?

I find it confusing that sometimes other members’ looks are praised way more than the visuals. I recently got into IVE and all I ever see in comments is people talking about how gorgeous Liz is (which I agree with of course) but people aren’t talking about Wonyoung’s visuals. Idk, I hope my question makes sense🫠