Hm the lifeless universe we observe. Uh unless you include observing earth. Duh. Also, outside of our solar system I’m unaware of “observations” sufficient to determine other planets are lifeless. In fact I’m certain we have no such observations.
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This is the point I always make. Life being extremely rare fits every observation we have so far.
The proportion of biomass to mass here on Earth is actually very small. It took life over 3.5 billion years to appear on land. And there are multiple critical events in evolution that occurred only once or very few times.
One thing we do know for sure is that life is possible in the Universe, because we’re here.
I think that the big variable in the Fermi / Drake analyses is time. The amount of time that we have produced anything observable to any other civilization is MAYBE 100 years, and our electromagnetic footprint may actually be getting smaller as communication goes from analog to digital and from long wave to very short waves. And, how long has it been since the last above ground A-bomb test?
Worse, there is a component in many of these types of equations that posits that any being that progress enough to be observable is necessarily descended from aggressive predators. So, the number of years that have gone by between us fighting with muscle-propelled sharp and blunt instruments to having the capability to destroy ourselves has been less than a millennium, still a blink of an eye in cosmological time. Some have theorized that any predator-based species will eventually and certainly acquire the means to destroy itself (which ours probably will). So, TWO civilizations existing at the same very short timeframe capable of observing each other would be almost impossible.
OTOH life has been discovered in the strangest, most inhospitable places on Earth; some of it doesn’t even depend on solar power like we do (those creatures that hang around smoker vents in the deep ocean are actually “powered” by the nuclear energy and heat of the Earth’s core).
So, I believe that life is probably fairly common in the Universe - but “intelligent*” life may be rare and fleeting.
*If we are so darned intelligent, why will we probably eventually destroy ourselves?
I could be wrong but I don’t think the ratio of biomass to the mass of the earth is a significant factor. The surface and oceans certainly seem to have lots of life, even if they are outweighed by non organic matter even on the surface.