When I was trying to get into acting, to have been a model was about as low as you could get in the acting profession. But that wasn't sexism, it was snobbery, which I knew and took very humbly.
In some instances, a gender imbalance is indeed a manifestation of sexism. In others, it is not.
Micro sexism can grow into a much greater problem.
There was really quite a remarkable level of sexism on newspapers when I started.