When you design a female character who isn’t conventionally attractive, you’re saying “This character doesn’t have to look pretty, they can still be good in their own way,” which is totally fine. I’m okay with people doing that.

But when you take a female character who was originally conventionally attractive, and purposely redesign her to be unattractive, you’re really just saying “I don’t like that this character is pretty, she isn’t allowed to be pretty,” You’re implying that being attractive detracts from a female character’s worth, especially if you consider the ugly redesign “better” simply because it’s ugly.