Two thoughts.

1) Our ancestors only lived to about 35 largely because of diseases we regularly avoid today, with better hygiene practices, vaccines, and antibiotics. The reason they boiled water to drink tea, mostly drank beer and added rum to their water was because these practices would kill off bacteria. (Don't do the rum thing. You'd need it to be stronger than you'd think. They drank the rum relatively watered down but were drinking it because it's rum.)

Primitive populations also would place their villages in places with known clean and safe water sources.

City dwellers also lived in filth. London had cholera and many other hygiene related epidemics quite often. These would kill off huge swaths of the population. Attempting to understand the reason for this was a big step in understanding germ theory and not the "foul air" of the outside leading many to keep windows closed during still nights. London's epidemics happened because water sources were downstream from river sewage disposal. The wealthy tended to be further upstream, while the poor were drinking their sewage.

2) Show me an untainted wilderness. You can't. They are gone. The most remote you can get in the lower 48 is 15 miles from a road and at no point are you more than a 1-hour drive to the nearest McDonalds.

The result is we've introduced pathogens into the wilderness that simply weren't there generations ago, and we facilitate their moving about by living near them.

There are things we can do to minimize pathogen problems, practices used by our ancestors that we can still be followed in a pinch.

Avoid stagnant water and opt for free fast running water. Know what's going on upstream. If you can get right to a water source, like an artesian upwelling of water, you are probably looking at some very clean safe water. In relatively pristine wild places, you might have an excellent chance of getting away with it, while a mud puddle in the desert with scat and flies is a very bad bet.

You can die relatively quickly from dehydration and the bugs you might contract can often be cured with medical intervention after you've been rescued from the emergency. Do what you gotta do.