how true is it that humidity drains, feel so it tires a person?

your question is poorly worded but people in high humidity do report less energy on average. but it is not due to the inability to make sweat, you can sweat just fine, after all it is the body pushing water out of the sweat glands. rather since the air is already laden with water the sweat does not evaporate and take the heat with it. so your body is unable to rid itself of heat as easily as it would in a climate with less humidity.

Your question is muddled, but I think you are asking if high humidity somehow tires a person. I believe the effect of high humidity is due to reduced ability on the person to sweat and otherwise lose heat.

it's called heat exhaustion. if you don't fix it, it can kill you