You seem to have created a little bit of a strawman in your first paragraph. You said that people are starting to argue that we could be the first in the galax

You seem to have created a little bit of a strawman in your first paragraph. You said that people are starting to argue that we could be the first in the galaxy, and then asked somebody to defend the claim that we are the first. Honestly, I don't think we have nearly enough information to be able to put much confidence in our ability to calculate a meaningful probability of life currently. Drake's Equation is fine, but without any way to validate the coefficients, you can make it say anything you want.