We're only about 5.5 billion years away from intelligent species being either very common in this galaxy, or completely nonexistent.

Which is to say that we need to start building interstellar transport vessels soon.

The key insight isn't the substituion of new numbers, it's the use of probability distributions with error bars throughout the calculation, as opposed to picking a single number. The canonical paradox is that even if you pick very small numbers for all the unknown terms, the resulting expected number of communicating civilizations is still high. This work shows that it isn't a paradox when viewed through the lense of a probability distribution, because even if the expected number is high, that's because of a long tail of super high, low probability numbers, while most of the probability is actually on 'alone in galaxy'.