Cannabis grows in full sun naturally, not a shaded forest where the soil will be mulched. It does not grow in swamps either. Without human intervention, the soil doesn't have anywhere close to as high a nutrient concentration than if chemical nutrients are fed to a plant. Tropical and subtropical climates don't exist naturally outside of subtropical and tropical regions, barring places that are given warm air from ocean currents.
Since you bring up swamps/lakes/rivers, that would mean hydroponics happens naturally too. In other words, this is a completely moot point.
So, I guess you're right. In nature, plants grow in plastic buckets with an electrically powered airstone, while swimming in a chemical slurry of nutrients and hydrogen peroxide. This happens All the time. My mistake. I need to research more.