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.
Why would they eliminate the competition if it was way behind in technology? Do we eliminate uncontacted tribes because they might be “competition”?
If aliens exist they probably have rules against interfering with primitive species. We are more like a band of chimps than an uncontacted tribe.
We don’t eliminate uncontacted groups any more because we’ve contacted everyone we want stuff from, and it didn’t work out well for them. Lower technology groups in the 1800’s submitted or were killed off. In a finite universe, any competition could one day try to take you out, so you take them out.
I don’t believe anyone can fathom another alien race, much less assign them ethical rules about interfering with other species. And apes are slowly being driven out of their habitat as we continue to expand.
Who said that they eliminate competition that’s way behind technologically? They haven’t eliminated us, so apparently they don’t. But it seems plausible that they eliminate civilizations that are on the verge of becoming dangerous - still a great filter, but probably a bit further in the future.