The problem is, due to the anthropic principle, we cannot say that the occurrence of life is average, because there is an inherent selection bias there. If life didn’t exist on earth, we wouldn’t be here to observe it. We only come into existence where life already is, and so we do not have a true average planet. To have a true average planet, we would have needed the ability to come into existence on a lifeless world. The cosmological principle actually doesn’t quite hold, because we are in a privileged position, as we, by definition, cannot come into existence where there isn’t life. This includes the kind of universe we exist in, as well, if multiple universes exist.

So, from our existence we cannot form any conclusions on how common life is. At best only an educated guess. If we detect life on another planet, only then can we begin drawing conclusions, as in that case we avoid a selection bias.