Not only are you the arbiter of relevance you are also perfect and the arbiter of the meaning of the word evolution. I guess all the actual biologists got it wrong.I agree. In biology, "evolution" refers to facts such as mutations, natural selection, changes is gene frequency within a population, horizontal gene transfer - but it doesn't refer to the concept of a Universal Common Ancestor (UCA). So yes, evolution is certainly useful in medical science.
By the way when you talk about UCA are you talking solely about our furthest common ancestor? Or are you ruling out all ancestors. Like do you believe in hereditary diseases? Or do you believe mammals share a common ancestor but not fish? Just trying to make sense of where you decide to draw the line? And what would count as an answer? I mean would the only satisfactory answer be that first ancestor of all life and without that you just aren't going to accept it?