[throwup238]

I’ve gotten the impression from several practicing archaeologists that the biggest reason they haven’t unified a bunch of the Homo species is that no one can quite agree on how to do it and there’s so much inertia in the field. Between ample evidence of interbreeding, the growing evidence that our genetic differences weren’t that significant compared to modern variability in the human gene pool, and a reevaluation of morphological differences it’s getting harder and harder to justify keeping them separate.

[Amezarak]

As a sibling comment mentions, this is true for pretty much all animals. It's a well-known, old problem. Darwin even mentions it in the Origin of Species and says that "species" is really just a term of convenience applied somewhat arbitrarily according to the different tastes of different naturalists.

Now we understand even better that, like GP said, there are no discrete groupings we can label as a species. It's a useful abstraction at a 5000ft level but it breaks down when you zoom in.