I live in a pretty hot climate, but it’s only really unbearable at times due to shoddy building and bad urban planning. Even then, summer can be difficult.
I can’t imagine what it’s like on the equator, especially in dense urban centres.
What’s Mumbai, Bangkok, or Singapore like at the height of the wet season?! How do millions of people function day to day?
Your perspiration into dry air has an evolved cooling effect. It's the same principle used by the 'zeer' pot to keep stuff cool in high temps with no electricity (and that's a freaking magic trick, lemme tell ya).
But, now see why the rising "wet bulb" temp is an issue in the lower US and toward the equator with the rising temps: if it doesn't evaporate, you're in trouble.