Personally I think there are plenty of hints (going back to Viking lander experiments) that there is simple life on Mars. However, there's a cultural reluctance

Personally I think there are plenty of hints (going back to Viking lander experiments) that there is simple life on Mars. However, there's a cultural reluctance to consense on its existence, unless absolutely positively certain. Fears like yours, about what Martian life could imply about the uniqueness and longevity of our species, are part of the reason for the reluctance. Note that if life is confirmed on Mars, it needn't have independently evolved. Simple life might be more common, even dormant in interplanetary space, than generally believed – seeding both Earth and Mars from earlier sources. (This is the theory of "panspermia".) Or, the same collision processes that brought the Martian-meteor with maybe-fossils to Earth, could have carried live spores between the planets – so a single microbial-evolution inside our solar system could reach multiple planets. Of course then your Fermi fears still apply. ("If microbial life is so common, why are broadcasting/traveling civilizations rare?") But it would mean the 'great filter' applies after, not before, microbial life.