I think this misconception might come from a once-popular book “Rare Earth” published in 2000. It based its whole logic on a premise that with current telescopes we haven’t seen many planets and that must mean planets are extremely rare.
It was already largely bunk at the time of publishing, but we have gotten better telescopes now and seen that planets are not rare. We just couldn’t see them with the old stuff.
I have this book. That’s not what it is about.
It is about how rare intelligent life may be. It assumes many planets.