It's been pointed out how in the Avenger movies, Thanos wiping out half of all life in the universe having the effect of disappearing half of humans didn't really make sense, cause it would probably mostly take out insects, or maybe there's a small handful of planets that contain majority of individual lifeforms that would take the brunt of that.

I suppose it's implied it was "half of life" on a per-species basis. It's basically magic, so probably best not to think about it too much.