Love the dress on her and love her in yellow!! IMHO, without the belt, the dress wouldn't have looked as sophisticated, which is I think the look she was going for as well.
My absolute favorite so far is Melania in this yellow dress. Notice no belt and how the dress is more formal looking - a belt would have made it look more 'business' like.

I wish someone had seen fit to photograph the entire dress and not just waist-up.
Re: the belt controversy, I think Michelle was trying to create a waist with her belts, while Melania already has one. Melania seems to be a little short-waisted, so the hugely thick belts, like the gold one, are overpowering. But if they're not as wide, and the same color as the dress/suit, they look pretty good.
I still love that black sequined number she wore to, I think, Trump's first speech to Congress.