Without digestive enzymes and oxygen therapy I believe that we can take all the herbs, supplements we want and most is not absorbed even if at all.
That's not true. In fact, oxygen therapies need to be done away from herbs since they can oxidize the herbs rendering them useless.
As far as enzymes go the ones that substitute for the body's own enzymes shut down the body's production of those enzymes. And your amylase, pectinase, cellulase and hemicellulase all increase the blood sugar. Might as well go feed on Ding Dongs for your cancer.
Then there is the fact that the later three enzymes mentioned above digest the food the flora that make up a significant portion of the immune system need to feed on. Therefore, they can be considered immune suppressants.