It's absolutely not mostly alive. I'm getting contradictory numbers, some say up to 55%, whereas encyclopedia Britannica says 30% of your feces by weight, and a huge proportion of those are dead. But regardless, your intestinal flora that lives on and feasts on your poop, and some of which gets excreted with your poop, is not the poop itself. I was mostly just making a joke, but your poop itself should not be alive. That's like saying the planet earth is alive because it has trillions of living organisms on it.