As a rank amateur, I have a question. Is the question of speciation a useful construct anymore? I mean, birds are dinosaurs and (some) dinosaurs were birds.

There is Neanderthal and Denisovian DNA in Homo Sapiens. Is the definition of what is a species tantamount to the legendary medieval argument of how many angels can dance on the head of a pin?

I'm not trying to be snarky. I'm curious as to the usefulness of the way we're approaching categorisation.

Genuine, but ill-informed, question.