There is of course the (admittedly astonishingly unlikely) chance that we're first. I mean someone has to be the first ones up, and since life on other planets is looking more and more factual other intelligent life should be around and other intellegent life if it was more advanced than us should be MUCH more advanced and we'd see evidence of them changing the galaxy. Since we don't well, maybe we're first.
One thing that doesn't really get brought up enough is the transition from intelligent life to advanced civilization. Due to our sample size, it is impossible for us to even make a rough guess at the odds of a successful transformation from one to the other. It is possible that we are significantly overestimating the odds of intelligent life successfully making the transition.
And keep in mind we are only part way there as well. It is possible that something like climate change (or some other natural/man-made disaster) ends our society before we ever achieve sustainable colonization.
