Ideally you would have a mulch layer, because you are correct if you are constantly taking out and not putting back you will have nutrient deficits. I take almost all of my defol leaves and make a mulch. I also have worms in my soil so they are constantly adding a source of nutrient.
But if you do it right you will have the right balance of life in your soil in terms of bacteria and fungi that will allow the soil to provide a canvas for cannabinoids and terpenes to express themselves more freely than a soilless grow. Like why does the Emerald Triangle produce superior product...the terroir/soil of old growth forest.