The parents in Marriage Story tried. And when the mom is unable to read the things she loves about her husband, we see her hot flash of realization as she leaves the mediation without engaging in the process.
My belief is moms and dads should agree that they will both ask for 50/50 custody in the case of a divorce. My agreement is more of a set of vows. I have not written a legally binding contract, like a pre-nuptial, that governs the money in the case of the divorce. I have written an agreement that governs the promise between the two parents to share the love and parenting of their children in a balanced way for the rest of their lives.