Thermodynamics and entropy, while causing decay in the long-term, have nothing to do with human decay over the span of 80-90 years.
Arguing that entropy is THE fundamental cause of death just shuts down the conversation.
A "causation" is an illusion. We can think, for example, that cause of ageing is in the evolution: those species who lives longer have slower evolving rate, and they lose a competition with other species who have shorter lives. But this causation does not contradict to the thermodynamic one, it just make thermodynamic not the "fundamental cause" but the mechanism of ageing.
A causation is the way to describe reality, not the fundamental feature of the reality. And so, the causation should follow the goals of researchers. While searching for ways to live forever, we will not benefit from evolutionary explanation (we cannot fix evolution to get longer lives), but thermodynamics explanation could be useful (if its true, of course). So, thermodynamics is a good candidate for the role of "fundamental cause".
