I was in Dubai from the 15th to the 19th of May, 2018. Ramadan started on the night of the 15th.

I can guarantee you that everything wasn't closed, but was as I described in my post above. As I said, places may have looked closed, and some definitely may have been, but many of them would have actually been opened but just had their windows blocked off and doors closed so people couldn't see in. Same for the food courts.
(And as a bonus to being in Dubai during Ramadan, I scored a free upgrade to a 3-room suite at the Conrad for less than US$100/night+tax!)