1. There are many ways to define species: https://en.wikipedia.org/wiki/Species#Definition

2. We can't actually test sexual reproduction of extinct "species"

3. Even if we go with the one definition of species which is "largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring", evidence of some reproduction does not speak to how often such reproduction led to fertile offspring. For example "No evidence of Neanderthal mitochondrial DNA has been found in modern humans"[1], and "Neanderthal males might not have had viable male offspring with Anatomically modern humans females"[2].

[1]: https://en.wikipedia.org/wiki/Interbreeding_between_archaic_...

[2]: https://en.wikipedia.org/wiki/Neanderthal_genetics#Interbree...