I know I went overboard at times and I ended up feeling betrayed at times...by my husband for not stepping up at times...and by my SD when she decided to sign on to her mother's lies and joined in her attack of me, despite all the sacrices I had made for her over the years after he mother left her to go live with an internet boyfirend and I nurtured her through that heart break.
In the end, the kids have 1 mother and 1 father. Just as I did, the mom in this case being a bit "codependent" to the father to some degree. If dad and mom are always going to just be at best mediocre parents, then that's just how it is. The step parents involved can't change it.