By law of conservation of evidence if detecting alien civilization makes them more likely, not detecting them after sustained effort makes them less likely, right?
Counterevidence for 2 - there are extremely few sustained reversals of either life or civilization. Toba bottleneck seems like the most likely near-reversal, and it happened before modern civilization. You would need to postulate extremely high likelihood of collapse if you suggest that emergence is very frequent, and still civilizations aren't around. If only 90% of civilizations collapse (what seems vastly higher proportion than we have any reason to believe), then if civilizations are likely, they should still be plentiful. Hypothesis 2 would only work if emergence is very likely, and then fast extinction is nearly inevitable. After civilization starts spreading widely across star systems extinction seems extremely unlikely.
Counterevidence for 3 - some models suggest that advanced civilizations would have spread extremely quickly across galaxy by geological timescales. That leaves us with:
My rating of probabilities is 1 >> 3 >> 2. And yes, I'm aware existential risks are widely believed here - I don't share this belief at all.
Countercounterevidence for 3: what are the assumptions made by those models of interstellar colonization?
Do they assume fusion power? We don't know if industrial fusion power works economically enough to power starships. Likewise for nanotech-type von Neumann machines and other tools of space colonization.
The adjustable parameters in any model for interstellar colonization are defined by the limits of capability for a technological civilization. And we don't actually know the limits, because we haven't gotten close enough to those limits to probe them yet...
We have a sample of one modern human civilization, but there are some hints on how likely it was to happen.
Major types of hints are:
Data for:
Data against:
To me it looks like life, animals with nervous systems, Upper Paleolithic-style Homo, language, and behavioral modernity were all extremely unlikely events (notice how far ago they are - vaguely ~3.5bln, ~600mln, ~3mln, ~200k or ~600k, ~50k years ago) - except perhaps language and behavioral modernity might have been linked with each other, if language was relatively late (Homo sapiens only) and behavioral modernity more gradual (and its apparent suddenness is an artifact). Once we have behavioral modernity, modern civilization seems almost inevitable. Your interpretation might vary of course, but at least now you have a lot of data to argue for your position, in convenient format.