I don’t believe this conclusion and I’ve read quite a bit on the subject...but I’ve been wrong before.
If there are that many inhabitable planets then even if only a tiny fraction developed intelligent life that would still be a great deal of planets. Where are all the signals of intelligent civilization then? We should be bombarded with radio waves shot off from long extinct, not so long extint, and even perhaps a few still extant civilizations. The silence is deafening.