You make a plausible argument, but your inferences are much too sweeping. There are millions of organisms on Earth. A designer that made each one a completely different, molecularly unique type of organism would have created an essentially magical world. It is at least equally plausible that a designer would prefer a universe that was rules based and logically ordered. And-- a big leap here -- if such a designer were actually concerned with us, he might particularly value a universe that is, at least in principle, somewhat predictable and comprehensible to human beings. It's getting too late to develop the argument now, but the idea of directed evolution is a step in that direction. There is nothing implausible about a designer reusing effective tools. If you were writing computer code, you would not deliberately set out to create bloatware. You would probably value parsimony in design. (Or whatever term the computer people use for lean, mean, efficient coding.)
None of this is evidence for a designer. But it does suggest that biological continuities are perfectly consistent with a design hypothesis. They should certainly not be taken as evidence against design.
Speaking for myself only, I use the term "elegant".