Copying what I said long ago, back during Akali release.
Let me remind you of our premise: By default everything is male. Now, if we needed a female ninja, we are required to do something about our premise. It has to remind us about the fact that the champion is female, not male. And what is the most powerful tool to use to convince that something is female? Yes, the female body!
Male body is pretty simple. They can be almost any shape. Thin like Singed, top-heavy like Mundo or bloated like Gragas. All of these three have in common is that while they are all so different, they do not change direction, in other words, they don't have dominant curves. You can really go to town with male bodies because it is so easy to avoid curves, you can make them like Rammus who is just one big Rolly Polly Ball or Blitzcrank with his enormous fists. But female body defies this freedom. No, female body is anything BUT flexible.
Dainty arms, dainty feet, shoulders are not broader than hips, hips in general, waist, things, breasts, female face, different body proportions, AAAAAH! Rammus would not work if we suddenly slapped breasts on him, neither would Mundo. You can't have diversity and artistic freedom when you are tied by all these stupid laws of biology. Designers are forced to operate between two extremes, human or non-human. Kinda human looking humanoid female does not work, it is just extremely hard to incorporate all those rules into anything special. You either go Anivia route and convince everyone that something totally not-humanoid is female, which works most of the time because we can easily accept it because they are not human at all, or just make another generic woman. Just try to brainstorm a female Gragas or male Evelynn, try. I am waiting.
And this is completely natural, you can see it every single game. Look at Dragon Age, where extremes could be seen in the Spirit of the Forest and Broodmother. or World of Warcraft and how male and female Orcs and Trolls work.
Creative female designs are lot harder to produce because by default, everything is male, even objects without any gender. To make something female, you must instill it female qualities. Thus we are forced into sexism, because human mind is biased towards masculinity.