Art of humans has always been idealized to a degree. This idealization of the human form goes back hundreds, if not thousands of years. Think of Roman or Greek statues. They reflect a kind of "perfect beauty" that can't really exist in real life, because let's face it, the human body can be gross and unappealing. Their idea of "breaking social norms" boils down to completely misunderstanding why humans are portrayed in such an idealized form in media (among other things, like the things you brought up or wanting to be seen as progressive).
Hence, why you might see an overweight character in a cartoon, but they don't have stretch marks, cellulite, or excessive fat rolls. They exist as an idealized form of being overweight, which usually is done by drawing them as being round or soft looking. Shapes and form can do a whole lot for characterization, and to an extent, you can tell what a character is all about based on how they're drawn.
It's beautifully ironic when people try to add a touch of realism to their art by adding "average human body grossness" to their art, only for them to draw a character that looks so bafflingly abnormal that they no longer look like a human that could actually exist. Hell, sometimes they just don't look like the actual character anymore, period. I personally prefer not to be reminded how gross the human body can be.
