i don't see the connection. being the only intelligent beings in the universe (at the moment) lends credence to the great filter, and finding large numbers of other inhabited planets eliminates it, and in between why wouldn't it monotonically decrease?
the idea is: if we do find life elsewhere, especially basic life, it suggests that getting to that stage isn't super rare. which means the great filter probably isn't behind us (like abiogenesis or single-cell to multi-cell jump), but possibly ahead of us - maybe in surviving long-term, avoiding self-destruction, spreading beyond one planet, etc.
finding life doesn't eliminate the great filter - it raises the unsettling possibility that we haven't hit it yet.
The argument you're referencing is usually about finding life on a nearby planet, e.g. on Mars. Nick Bostrom has articulated [0] this argument. But finding life on a distant planet lacks the same statistical power for instilling this existential fear.
Of course. It'd be much worse if we found life on Mars than on a distant planet. In either case, the chances of humanity being ahead of the "great filter" are greatly reduced.
