I personally think a lot of stepparents on here are low-key awful. But you have the patience and kindness of a saint. Their room looked amazing after you cleaned it up. You don't do that for kids you don't care about.

I will say though that a surprising amount of people live like your stepdaughter's. They would insist that the condition of your stepdaughter's room is just a preference. So maybe that's where this commenter is coming from.

Who is picking on kids?

Your husband. How could he blame your 5 year old when their room is always a mess? I would also bet your five year old has a cleaner room and better habits.

To me it seems obvious he's the inferior parent but so insecure about it that he sees doing anything different as an admission of fault.