Chicken pox is caused by the varicella-zoster virus, which can certainly be fatal if contracted as an adult (i.e shingles) and never been exposed to it as a child. _Now_, most people are exposed to it when they're children, when it's much less serious, but vaccination is still the preferred method because it can still be deadly in children in certain cases.
FYI, ~6.4K people still die every year to chicken pox and shingles. It may seem comparatively small, but that's still people who die. Before a vaccine was created, it was around 4x that.
Vaccination has empirically been shown to reduce the number of major hospitalizations and deaths as a result of the virus. It's an injustice to undermine _any_ number of lives potentially saved or thousands in hospital bills avoided because you believe science is "quackery".