I could say a lot about this. I’m sympathetic to a degree - I had really rough postpartum depression and motherhood was a hard adjustment, and I also really wanted kids. And some people are better at some ages and stages than others. I stink at toddlerhood, although I’m getting better.
The “backlash” against publicly expressing this kind of thing is, IMO, appropriate. For one thing, children aren’t likely to understand the fine distinctions these mothers are trying to make, and two, what’s the point? They’re here. Deal with it. Make the best of it. For generations we understood that we had to live with the consequences of our actions (and sometimes the actions of others.) If you have to hash it out in therapy, please do. But don’t make public statements about loving your children less than your spouse or wishing you hadn’t had your children. That’s a really, really $%^&% thing to do, even if it’s true. Miss Manners is on to something when she says it’s a mistake in our society to think we have to tell people everything we think and feel.
I think in a society where children were more present and mothers were more a part of the community, this kind of phenomenon wouldn’t exist even in the small way it does now. There’s always been bad mothers (and fathers). But a few generations ago it was easy to get a break from a neighbor or relative and you had other people around you all the time even if you stayed home with your kids. That’s not the case now.

Maybe address that instead of wishing people didn’t exist.