The equation itself makes no assumptions. But anyone trying to calculate something with it must.
The last five factors in the equation will be filled in by assumptions based entirely on one data point, life on Earth. From your link:
ne = the average number of planets that can potentially support life per star that has planets.
fl = the fraction of planets that could support life that actually develop life at some point.
fi = the fraction of planets with life that go on to develop intelligent life (civilizations).
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = the length of time for which such civilizations release detectable signals into space.
Can you define any one of those without assumptions, in a scientifically proven way?
The last five factors in the equation will be filled in by assumptions based entirely on one data point, life on Earth. From your link:
Can you define any one of those without assumptions, in a scientifically proven way?