You've not accounted for the tiny number of observations that we've made nor the limited power of our observations. We're not even sure if life existed on the planet literally next to us, let alone these exoplanets. Otherwise I could argue that all observations are consistent with a probability less than 10^-10 or 10^-20 or any other number I feel like.

Ask yourself this, from how many planets in the universe would you be able to observe life on Earth?