Why divorcing a spouse for irreconcilable differences is unconstitutional?

I have written a book on unilateral/bilateral contract law in regards to marriage, divorce and remarriage. According to the law, contracts MUST be enforceable. They can not have subjective opt-out clauses. Otherwise, this would not be classified as an enforceable contract, but simply a non-binding agreement. Therefore, when someone says they are dissolving the marriage for irreconcilable differences the burden of proof falls on the plaintive to show it was done in good faith. NOT the defendant to prove it was done in bad faith. The marriage license makes divorces subject to strict contract law. Therefore, counseling would be needed to show there was sincere effort by the plaintive to keep the marriage together, as in a business contract with opt-out clauses needs to show there was good effort to keep the contract intact with mediation.