It's a fair question, and worth asking directly rather than skating past: doesn't bringing God into the middle of a marriage crowd out the relationship itself? Isn't marriage, at the end of the day, between two people?
What the wedding actually declares
Ask someone what happens at a wedding, and the answer is usually simple: two people commit themselves to each other. True, but incomplete. According to Scripture, God is present at that altar not as an invited guest, but as the covenant's author and witness — the one whose purposes give the ceremony its meaning in the first place. Malachi describes God as witness to the covenant between a husband and "the wife of his youth," language that assumes his ongoing, active involvement, not a one-time blessing at the start.
A third party that strengthens, not competes
Here's the part that resolves the objection: a third presence in a marriage doesn't have to mean a crowded relationship. It depends entirely on what that third presence does. A meddling third party divides a couple. Christ, rightly understood, does the opposite — he's the reason a husband can love sacrificially and a wife can extend grace that isn't naturally available on human strength alone. Far from competing with the relationship, his presence is what makes the healthiest version of it possible.
Where this goes next
So no — marriage was never meant to be run by two people alone, asking God's blessing from a comfortable distance. It was always meant to be lived with him present in the middle of it. That's not a diminishment of the relationship between husband and wife. It's the very thing that gives that relationship its deepest strength.