If this isn’t true, and life is actually common throughout the galaxy ... then the great filter might still be ahead of us — such as not surviving technological adolescence. Meaning we’re not special, we just haven’t died off yet.
Great filters start with the observation that we have detected no signs of alien technological civilization. The assumption is this means they’re rare.
In other words, even if the average technological civilisation lasts 1000 years, the odds of those civilisations overlapping are nearly zero if the great filter is ahead of us. Unless civilisations manage to last much, much longer than 1,000 years (millions of years), the chance that two blips overlap in time and space closely enough to detect each other is basically negligible.
That is why the “life on Mars” point feels ominous:
- If abiogenesis is easy, the filter isn’t there.
- If the filter is later (like surviving technological adolescence), then most civilisations blink out quickly.
Which means overlapping, detectable civilisations would be vanishingly rare, explaining the silence, but also suggesting our future may be short.
Personally I think the great filter is a dumb idea for precisely the reason you posit. The universe is (probably) infinite, which means there's an infinite probability that we aren't special or alone. Maybe we're the first; the universe is (relatively) pretty young from what we can tell. I doubt that too, but I think it's one of the most plausible explanations.
But really what it comes down to is that in an infinite universe, the probability of anything happening exaxtlt once is infinitely small. It is infinitely more probable that there is or will be other life out there.
Really, out of uncountable trillions of planets in trillions of galaxies across tens of billions of years, how could it be that exactly one planet can produce life? I think it's egotistical navel-gazing in the extreme to assume we're alone.
We aren’t special. We will die off.