Conversely, I can tell you about two parents who did not seperate when they should have.

We started out thinking we only wanted to live with dad because he was the "fun" one.
By preteen age we were learning dad was sneaky and manipulative and only fun if he got away with it. I started asking mom why she didn't leave him and never got a good answer. As an adult I think she just didn't want to bother.

We loved dad but strongly resented him. He lied and cheated and was horrible with money, leaving mom only as the enforcer. We didn't respect either parent for a long time. Dad for being horrible and mom for not having the stones to do anything about it either for herself or for us. Dad passed and we're now on good terms with my mom and love her through her faults.

We all struggle with what's considered "normal" to put up with in a relationship and would much rather have had an example of what being happy, and having functional relationships looked like versus figuring it out through trial and error and repeating our parents mistakes.