As with many things: maybe no simple answer. The consensus is that we originated somewhere in East Africa, which is generally less humid, and the climate may well have been quite different then anyway. So, it is likely that there was less exposure to protracted high humidity, meaning that we never really evolved to deal with it. As a result, though there is enormous variation in modern humans (both in physiology and behavior), the majority still are more comfortable with a moderate humidity level and air conditioning provides it along with the reduced temperature.

We need to maintain a core temp of 98 degrees. Why this is so is another discussion.

Usually our skin temperature is about 85 degrees.

When the temperature is 98 or above, we are under stress.

High humidity, high dew point, is a factor. When the dew point is 90 or higher, sweating doesn't work very well, since the lowest skin temperature we can achieve by sweating is the dew point.

The body can't shut down it's metabolism to stay cool, so the heat produced by the human body, about 60 to 100 watts of heat, has to be dissipated. Even if your pretty well adapted to a hot climate, there is still the need to dissipate the heat of metabolism.

In air-conditioning, not only is the temperature reduced but so is the dew point. So then when we sweat, we can easily make ourselves comfortable.