The fact that you even use the term "herbivore male" unironically says more about you than the series.
Yeah, it'a generic, but so is most stuff, especially isekai or power fantasies. If you don't like it, don't read. That's what I do.
The mom seems like a classic case of a malignant narcissist. Has a golden child and a scapegoat. Tries to live vicariously through the successes of her favorite.
And even if a child is a golden child, the moment they step out of line, the mom's abusive side would come out. Sometimes the kids...