Ugh. It is not unreasonable to take the Drake equation seriously. You just have to correctly understand what purpose it was supposed to serve. The equation is not about calculating the probability of intelligent life. It was about identifying what information needs to be gathered do that you can calculated the probability of intelligent life arising.

In other words, the equation was created to help guide research, not to answer the question itself directly. As a guide to research, I think the equation remains highly relevant.