What's the basis for that? Human civilization has always advanced in the long run even after periodic downfalls and has already lasted far longer than 1000 years. I think this is contradictory to a lot of the underpining of the belief in ETI. People tend to expect ETI to be advanced far beyond us yet if true why should their civilizations have such limited lifespans? This excuse for lack of contact is always glossed over in my view.

Couching it as limitation on use of radio isn't much better. There is no real scientific alternative as a means of long distance comunication other than something that travels at the speed of light. I'm not an EE, but don't see why if there was a better form of EM radiation to use for communication over long distances we wouldn't already be using it.

If you want to blame it on limited resources surely in a galaxy where evolution of intelligence is common on earthlike worlds at least one species would have the foresight to learn to use the much larger pool of resources in space. Calculations based on that and seemingly feasible transport show Fermi's paradox to be valid.

I believe earthlike worlds are much rarer than expected when the Drake equation was formulated. I also believe the probability that a technical civilization will evolve on an earthlike planet is much lower than 1. Another factor I never see is a proper balance between land and water. I don't believe mostly dry worlds would be climactically stable to maintain liquid water for long periods and too much water would inhibit access to the resources needed for a technological civilization. Planets much bigger than Earth will tend to be water worlds due to lower surface to volume ratio and smaller worlds will tend to dry out like Mars did due to weaker gravity.

The other key issue in long term stability is plate tectonics. No other terrestrial planet in our solar system has it and it is also crucial to concentrating resources and stabilizing our climate.

In short all these estimates that come up with some number greater than 1 for civilizations in our galaxy have some glaring over sites in my view.

If I had to bet, I'd place my money on life is easy, multicellular life difficult, and technology capable (ability+environment) intelligence a rare fluke.

Regards,
Mark