Brita filters most certainly do filter out "microbes". Just with low certainty that drops over the age of the filter.

It's not the microbes in my experience, it's the heavy metals suspended in the water.

It's like a 0.1% damage over time effect. A few days drinking it? Fine. A few weeks? Still fine. Months? I started feeling just a bit more sick until I cut it out for filtered water.

Try drinking tap water in Africa, India, Bangladesh, most of South America and South Asia, in fact most of the 3rd world... good luck. Ie India had (maybe still has) high infant mortality due to water-transmitted diseases. Once you can't effectively 100% separate waste water from natural water table or other sources for drinking, everything becomes contaminated.