I'm just going to say this once because we've hashed this out before, but you're wrong.
Like, it's very clear you have no idea how the real world works. Truly shitty parents USUALLY don't get better, but they can. Some actually do. I've seen it. I've actually seen much more abusive parents than these in real life get better. I've seen much more stay bad, though.
At the end of the day, it's up to the author to decide how to write this. My problem is that you made a statement about real life, and you're wrong.