Here's the bottom line for me...and understand that I'm still learning as I go and have failed in the past, but experienced grace and mercy and forgiveness and more and my marriage was restored to better than before...the bottom line is that if we're to believe the Bible, then it trumps all other examples of marriage as it has the earliest form of marriage on record; Adam and Eve.
So, it would seem "normal" that anyone entering into marriage would follow the standard set near the beginning of time, yes? Instead, we've allowed the world to redefine what is to be a holy commitment.
Just like everything else, if people can work the Bible out of the equation, the floodgates will open and alternatives to the "standard" will be offered up as normal. Have that alternative happen over and over and all of the sudden you get people who are supposed to believe in the Bible saying "I don't see the big deal in the alternative".
God didn't change the standard; we did.