Thank you for reading commenting, Reece.
Your questions make total sense — They’re 100% logical. Now, the Drake equation was never really meant to be a scientific proof. There is a ton of optimism there. I think it was meant as a way to help popularize the ideas behind it, and get people more excited about space exploration in general. See: https://news.nationalgeographic.com/news/2014/06/140630-drake-equation-50-years-later-aliens-science/
And then there’s the matter of how many civilizations might be using radio signals. Again, that is really nothing but an optimistic guess. But keep in mind it’s a % of the factors that came before it: fraction of planets that might be habitable that might support life that might lead to intelligent life.
The last 4 parts in the equation are all going to be guesses until we actually have some data to support them, which would mean some actual knowledge of life somewhere else in the galaxy.