If we’re willing to make assumptions about how likely it is that life arises on planets with certain similarities to a young Earth, we can indeed draw conclusions about the likelihood of intelligent life throughout the galaxy. The only problems are that our conclusions are only as good as our assumptions, which we have no reason to believe are very good. There may well be 36 alien civilizations in the Milky Way right now, but science has a long way to go before anyone — even the paper’s authors — are convinced of that conclusion.
https://www.forbes.com/sites/startswithabang/2020/06/16/36-alien-civilizations-in-the-milky-way-the-science-behind-a-ridiculous-headline/#30c845dd79c5