The problem with the "if you change this one little thing, life on Earth wouldn't be possible" line of reasoning is that life evolved specifically with the Earth's conditions in mind. Of course changing things around would be fatal for life on Earth. But life evolved to survive in these specific conditions, not any other.
There are likely trillions of worlds (including moons) in the universe, each with a unique blend of conditions specific to them. We know the vast majority of them don't have the conditions to host complex life as we know it, but eventually a world would have the specific mix of criteria just right for life as we know it to develop. The Earth is one such world.
More difficult questions arise with the "if you change this specific factor, the universe as we know it wouldn't exist" line of reasoning. Modern physics seeks to get around this conundrum with multiverse theories, but such theories are untested and perhaps untestable. That doesn't mean "God did it" is the correct answer, though.