It is a myth that historically people drank beer and wine to avoid unsafe water. People have always drank primarily water, there has never been sufficient production of any other beverage for all people to drink it as a replacement for water.

Also, consider the self-refuting nature of the statement: people didn't drink water because water born illness was too common. Water born illnesses were common historically because people drank water primarily. But as with all diseases, transmission and outbreaks are a complex dance of exposure, immunity, and prevalence. When a disease is modestly prevalent a lot of people will be exposed and acquire immunity, leading to reduced transmission, when a disease is less prevalent immunity will typically go down, laying the ground for a resurgent outbreak. Typically disease prevalence is a cyclical process, on various time scales. Meaning that even when the overall lifetime risk of getting a water born disease is high, from day to day it may not be high, and once exposed an individual may have a high chance of survival and gaining immunity (which is true even with diseases like cholera and typhoid).

Basically nowhere in the world was record keeping good enough prior to industrialization to be able to track historical levels of water born disease prevalence or burden. Making things even more difficult is that it's basically not possible to distinguish between the symptoms of many water born diseases without modern analytical techniques. In any event, disease of all varieties was so common throughout history that only the most noteworthy outbreaks (like plague epidemics) have been put down in the historical record, everything else is just part of the background of everyday experience. People broke their legs, people got sick, sometimes they died from getting sick.

As for what anyone did to improve water quality: generally nothing. The major exceptions were constructing aqueducts. Aqueducts bring fresh water from far away and are typically far cleaner than local wells or rivers. They also break the local fecal oral cycle of transmission that is common for many water born diseases. Nobody who built an aqueduct in ancient times knew of these factors, they just knew that the water tasted better and making use of an aqueduct was a way to provide plentiful water to an area that might not otherwise have enough fresh water for its population. The Islamic world inherited several aqueducts that had been built by the Romans and they built many of their own as well, but again nobody had a theory about water born illness back then so the public health benefits were somewhat accidental.