I'm sorry, but this is a very ignorant idea. Death and decay are 100% necessary and required for living things.
We are organisms that cannot produce our own energy from sunlight, thus we require plants to convert the sun's energy into compounds that we can break down to get our own energy. We piggy-back on plants and need them. Plants also piggy-back on bacteria, as we do as well.
Cellular death is essential to our survival. Here are some basic examples:
- The way we excrete iron is by exfoliating the cells in our gut lining. These cells die with excess iron so the body does not become iron overloaded (which leads to liver and heart failure).
- In embryonic development, the process of cellular apoptosis (programmed cell death) is utilized in forming many organs, and that is why we aren't born with webbed fingers.
- Apoptosis checks unnecessary cell growth. If you don't have apoptosis, you will develop cancer because DNA mutations occur at random, and apoptosis helps combat this.
We do need bacteria for more than just Vitamin B12. Here are more reasons:
- Vitamin K is not produced by humans, and our gut flora (bacteria) makes it for us. Our coagulation system absolutely requires Vitamin K for the synthesis of factors 2, 7, 9, 10, C, and S. Hard to see how you would be able to live if you were bleeding into every joint and muscle in our body because you couldn't form blood clots.
- Bacteria in the gut break down a lot of complex polysaccharides that our enzymes cannot, freeing metabolites for us to absorb that we otherwise couldn't.
- Bacteria detoxify micronutrient carcinogens that are ingested in the everyday diet.
- Small molecules secreted by bacteria help in the absorption of cations necessary for life.
- The interplay between bacteria and the immune system is extremely complex and could fill the dissertations of hundreds of PhD students.
The moral of the story is this: when we actually look at the biochemistry, genetics, and physiology of human life it becomes abundantly clear that we are fine-tuned for the environment that we live in. This is, of course, because we evolved in this environment. We depend heavily on bacteria, plants, and other animals in this world because we are part of this world and nothing else.
Frankly, I find your argument about the Fall to be rather infantile and ignorant. You clearly don't know anything about human biology, and seek to make your theology trump it.