What is minimized, if not ignored, by SETI enthusiasts are the particular features of Earth and our solar system important to life which imply the probability of life elsewhere in our galaxy is extremely small. Besides the size of the Earth and a habitable distance from the Sun, these features include its elemental composition, a sufficiently large amount of liquid water, the composition and thickness of Earth's atmosphere, the rate of rotation on its axis, the strength of the magnetic field, the amount of radioactive elements, the movement of the tectonic plates, the thickness of Earth's crust, the size, density, orbital distance and tidal action of Earth's moon, the nearly circular orbit of the Earth around the sun, the tilt of Earth's axis, the ratio of land-to-ocean surface area, the arrangement of continents relative to the slight eccentricity of the Earth's orbit and axis, the orbital plane of Earth and the other planets around the sun, the size and relative position of the large gaseous planets, like Jupiter and Saturn relative to that of the Earth and the inner planets, the orbital locations of asteroid and planetoid groups, the lack of large planets inside the Earth's orbit, the elemental composition of our sun, the age and size of our sun, the heliosphere of the sun, the position of our solar system with respect to the galactic arms, the relative position of our solar system from any supernovas, the location of our solar system relative to the galactic center, and the size and shape of our galaxy. No doubt more could be listed.
For each one of these features, (sometimes even small) changes one way or the other would result in conditions where life (or intelligent life) on Earth would be impossible or unlikely.
Can't disagree with you regarding the extremely long and unlikely chain of conditions necessary for earth-like life. Personally, I don't think we're going to see much life like it out there when and if we ever travel to the stars (and thank goodness for that!).