I first heard about this when I saw ragebait posts from chuds about an upcoming Pokemon Go update ERASING WOMEN 
Now that it's out, the new models do look pretty bad, regardless of your gender:
https://i.redd.it/hf02d07y64vc1.jpeg
My own avatar is a dude, and he now has the complexion of Gollum and a weird baby face.
At least if everyone hates the new avatars, the discussion will be about how the actual models look terrible and not be dominated by right-wingers complaining about the added inclusivity.
All i can really say for it is you can be fat, which is nice and most games won't allow fat people. Other than that pretty gnarly.
Unfortunately it looks like animations don't get adjusted at all to account for different body proportions so your limbs just clip through your body constantly if your sliders are cranked all the way up.
That's what you get in most games with body sliders. The animations are designed for a slimmer default size so everything just clips if your character is too big. What makes it different in situation like this is that the update was intended to make the game more representative and inclusive, so you'd expect some effort being put into making the new options not feel like an afterthought or something out of a meme game like Palworld.
