1) The majority of horseback riders are skinny, male and female but especially female. I used to work at a stables in Arizona, and believe me the women were skinny as poles. Yes, they had intense core muscles- but those didn't change their skinniness, and you really could only see them when they were riding. Let's be honest: you can't tell whether or not the new champion has a six-pack or not from that picture. tl;dr: She isn't unrealistic, just doesn't wear much clothes.
2) I think you are severely over stating the size of breast of quite a few champions. Many, like Caitlyn, Irelia, LeBlanc, Lux, Morgana, and Vayne have perfectly normal sized breasts for their body type. Are their body types themselves unrealistic? Perhaps. But not really, or at least not by much- and to be perfectly frank, theirs is a body type many women should prefer to the feminist-endorsed BBW stereotype which is not really all that health for the woman. No, I'm not advertising emaciation, but for crying out loud being big does not mean being beautiful, and there's a reason skinny is considered beautiful in many cultures- because it is healthy, and that leads to positive connotations. A healthy wife is someone who can be with you for all your days- a larger wife, who has more likelihood of high cholesterol and blood pressure among a thousand other problems, is much less durable. tl;dr: League of Legends women, with some exceptions (and maybe 5 exceptions is certainly not unreasonable) are realistic and reasonable.
3) Don't say that gender is an issue here. We have Ezreal, who is widely acclaimed for being easily confused between a tomboy and a legit guy, we have more male than female yordles, 90% of the "evil" characters (there's Morgana on the female side, and then Malzahar, the void creatures, Vladimir, the Noxian people, Shaco, Nocturne, Mordekaiser just to name a few on the male side), and then there are the unreasonable male characters: basically Pantheon, Kassadin, Nasus, Master Yi, etc who all have perfect bodies. So basically, male is just as messed up as female- don't go complaining about the female characters pretending they get all the stereotypes, because just as many if not more occur on the female end.
tl;dr: On the whole, Riot has done an amazing job keeping gender reasonably balanced and keeping the models for the characters rational and translatable to the real world, especially for a video game, and no one really has the right to complain.
2. Its a game, you completely missed the point of this thread, which is completely understandable because bahs can't really read .