We’re reasoning with averages here. Ever take a statistics course?
Of course it matters how often supernovae occur. If only one occurs every ten billion years, that is not going to be enough to prevent advanced forms of life from arising somewhere in a galaxy. But if a million supernovae explode every hundred million years, that could be enough to prevent vast regions of a galaxy from ever developing multicellular life forms.
Some regions may get lucky and escape, as we may have, but most won’t. That’s the reasoning.
“But if a million supernovae explode every hundred million years, that could be enough to prevent vast regions of a galaxy from ever developing multicellular life forms.”
But again, we have prima facie evidence that doesn’t happen, or at least, has never happened in the entire history of life on earth.
You keep neglecting to address that fact, and until you do, your arguments are pretty meaningless.