Steve, you make a fair point. First let me say the following: None of us know how rare or common life is beyond Earth. What we do know is that life is common and diverse on Earth, and that so far there is no sign of life elsewhere. It is not obviously present on other planets in the solar system, and if there is intelligent life elsewhere in our galaxy it is not doing anything to make its presence known in verifiable ways. We also now know that there are many rocky planets around other stars so the opportunity for extraterrestrial life to evolve is there.
My essay is a hypothesis for how things may have come into being. What I say in my essay are predictions based on that hypothesis, not claims of fact. I should perhaps have made that clearer in the conclusion but I reached the word count limit.
My statement about rarity is that intelligent life is rare beyond Earth. This is a prediction based on observations of fine-tuning and the accidental events that made our evolution possible. It is consistent with the absence of signals from extraterrestrials, but it could still easily be wrong and I don't intend to pretend otherwise.
I do think that primitive bacterial life could be much more common than intelligent life. Early bacteria on Earth would have modified the atmosphere. There were several mechanisms for producing oxygen before chlorophyll took over. Oxygen would not be maintained in the atmosphere without some biological mechanism. There is a good chance we will be able to determine whether oxygen is present in exoplanet atmospheres within the next few years.
I do think that present claims about Earth-like exoplanets is being over-hyped. It is easy to get optimistic about life being common because we would like it to be so. Perhaps it is common, but my prediction is that the circumstances that make life evolve to higher levels are very rare. I think your more optimistic view is more the norm now.