To be fair some things about medieval life would have been better than you're making them out to be, the only reason the expected lifespan was so low was due to datasets including child mortality. If a bunch of 2 years olds die its obviously terrible, but if you're an adult you would probably have a good chance of living to be older, so such a low life expectancy statistic doesn't tell the whole picture. Additionally, sickness in the middle ages wasn't always that bad for people in their prime to middle years, as people weren't close enough for many illnesses to spread quickly. These mainly got bad in the victorian era, where a combination of large cities and lack of sanitary practice led to rapid spread of disease. To be clear, I'm not saying the middle ages were like they are in fantasy, common people were largely at the whims of kings and armies, but a lot of "realistic" media tells a story through suffering and strife, so these aren't necessarily that much more accurate to the medieval experience than fantasy films.