The Great Filter is the idea that, in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
https://en.wikipedia.org/wiki/Great_Filter
The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, “If life is so easy, someone from somewhere must have come calling by now.”
https://en.wikipedia.org/wiki/Fermi_paradox
Personally I think it’s photosynthesis. Life itself developed and spread but photosynthesis started an inevitable chain of ever-greater and more-efficient life. I think a random chain of mutations that turns carbon-based proto-life into something that can harvest light energy is wildly unlikely, even after the wildly unlikely event of life beginning in the first place.
I have no data to back that up, just a guess.
Even if you had a super intelligent species that can make Dyson spheres and travel at the speed of light the observable universe is beyond vast. I don’t know much about cosmology or our ability to detect light but given humans have only been looking into the sky for a couple centuries, not being able to see a thimble in the ocean seems like a non issue. I think if you scale the observable universe down to the size of earth the speed of light becomes 0.05 mph.