Yes, that's a good point, and in fact astronomers are debating that, with some thinking we just need bigger, better telescopes to see more small rocky planets.
There are other problems though. Like that one earth sized planet we found at Proxima B. Unfortunately Proxima B is a red star (low energy), such that the only way to get sufficient light and heat is to be orbiting it at like half or less of Mercury's distance from our sun. Close enough that this planet is tidally locked with it's sun, like our moon is with earth, such that it's always day (boiling) on one side and always night (freezing) on the other. Also, ironically low energy stars have far more severe and frequent solar flares than larger stars.
All that wouldn't be so bad if red stars, which can have trillion+ year lifespans, weren't 70% of all stars in the galaxy. And the massive blue stars are another 10%. Those last a billion years or less before they nova, and they put out too much high frequency EM for their to be complex life orbiting around them while they last. That leaves the 20% that are mid sized yellow or yellow/white as possibilities.
All these filters - star type, planet size, planet composition, an unusually massive iron core, an unusually over-size moon, gobs of H2O, the lack of planet killing features like too much volcanism, and others make the probabilities of a given star system having life very tiny.
We know it's a low probability, but I suppose we won't know for sure how low until we can see more exo-planets.