See garciasn's sibling comment to yours.
Degree matters. A lot. Saying "it's universal" because there is some frequency everywhere is misleading. There are many country Xs that absolutely deserve to be called out as bad, because they are relatively so much worse than the best countries, or even the average ones.
My intent: "it's universal" means the correlation between girls being low-value and child marriages is universal.
Your seeming reading: "it's universal" means child marriage occurs in every country...but that is a huge tactical mistake to say, because it gets in the way of us condemning countries where the problem is much worse than in ours.
My concern is for the girls, not for scoring point for condemning countries. To actually help the girls, the article seems to provide a proven solution. So let's do more of what works.
Vs. what is the track record for major non-aligned nations (like Nigeria) implementing progressive social reforms at scale, in response to moral condemnation by foreigners? That I've heard of, not good.
I agree scolding generally isn't effective, especially when the scolding party has no power to enforce rules.
At the same time, I see no reason not to make the condemnation. It's not being made to effect change, but reaffirm our own norms which, in this specific case, I believe are better, and we shouldn't avoid saying so and call that enlightened. I think it's a form of cowardice.
And in this connected age, perhaps a Nigerian girl could take some hope, or energy, or solace knowing that much of the world does think the way she is treated is wrong, and not normal, and that her intuition to that effect has grounding, despite the powerful local norms she finds herself faced with.