The concept of a species is historic and has no equivalent in molecular biology. It was established in its basic form more or less 250 years ago when evolution

The concept of a species is historic and has no equivalent in molecular biology. It was established in its basic form more or less 250 years ago when evolution wasn't even a real concept yet. Sure, it has been adapted in so many ways but in the end is mostly kept nowadays for legacy reasons. I mean there are so many inconsistencies to begin with like are house animals their own species, the interbreeding you mention, when does one archaic species becomes modern etc. In the comments you have already gotten, the neanderthal people are referred to as a species, even though very often they are only considered a subspecies of modern humans. There have been successful interbreeding events while at the same time every child can distinguish a neaderthal skull from a modern human one. Svante Pääbo and his team intentionally declared Denisovans only as a genomic type but neither as a subspecies nor species.