I am certain there are more parents then we think who experience varying degrees of these feelings. Maybe just feeling dissatisfaction with their life- still loving their child but not enjoying being a parent. Or even more along the lines of what you described.
We can care for our child, love our child, while not particularly enjoying being parents, and even regretting it, all while still caring for and loving the child.
Our culture is not one that allows for nuanced feelings. If you feel dissatisfied being a parent, you are a "monster," you "don't care for your kids" and you are "unfit" as a parent.
Why can't you care for your child, even love them, while not liking being a parent? The answer is, you can. It's just that no one talks about it because our culture would never be able to be open to the complexity and nuance of such human emotions.