The methods used by astronomers to detect exoplanets around nearby stars all have severe limitations. These methods include

1)Transit. The light of the star is dimmed slightly by the passage of a planet between us.

2)Doppler. The spectral lines of the starlight are shifted from red to blue and back due to the gravitational tug of the planet on the star, caused by the primary being accelerated towards and away from us.

3) Astrometric. The star's apparent path through space wobbles, and/or speeds up or slows down as it and its unseen planet both revolve about their center of mass.

1) and 2) further depend on the planet orbiting its primary in an orbital plane that intersects our solar system. If the star passes above or below the star we won't see a transit, and there is a strong cosine theta term which makes orbits highly inclined to our line-of-sight to have quickly diminishing radial velocity components as the orbital plane tilts away from us.

Method 3) works better if the planet's orbital plane is perpendicular to the line of sight. (Wobbles are easier to detect than speed changes.)

All three of these methods tend to work much better on very massive planets orbiting very close to very small (unmassive) stars, so there is a huge selection effect that favors the discovery of gas giants orbiting very close to red dwarfs. An earthlike planet orbiting in the habitable zone of a sunlike star would more likely be missed.

Conclusion: considering these restrictions, the fact we've discovered as many exoplanets as we have in so short a time suggests solar systems are extremely common in our galaxy. It also suggests the average nature of these planets and their orbits is not well understood. Earthlike worlds in the habitable zone may be very common and we would have no way of knowing it from the data we have.

There is one unexpected bonus to this analysis. If extraterrestrial astronomers use similar, but more advanced, methods to ours to search nearby stars for planets, then we should concentrate our search for signals aimed at us (both microwave and optical) on our own ecliptic plane. ETs who suspect we are here and trying to get our attention are more likely to be clustered there than in any other direction. They would be the ones most likely to have detected transit or Doppler evidence of Sol's planets.