The issue is that of concentration. You need some kind of biogeochemical cycle that creates a concentration gradient. Otherwise the basic components are too diffuse to do anything meaningful.
I still lean into the "volitile ice balls" theory. NHx, NOx, Ox, etc. as volatile ices on asteroids in orbits where the iterate between freezing and melting. Moving between freezing and melting creates the biogeochemical cycle necessary to concentrate the basic elements sufficiently to be meaningful.