I have no idea about the current rules, but haven't they always been separate species? Can an elf and a dwarf make a fertile child?
But it came with stat hits. Half-elves were more like humans than elves, etc.
And from what it seems, they're separating stats from race/species. Which is probably an overall good. I'm going to use the older terminology as this was the issue with the older game. If you wanted to be a wizard, you should be an elf. If you wanted to be an elf, you should be a wizard. And things like that. Certain classes just worked better with certain races.
But now, if I want to be an elf barbarian, that's better supported. I'm not fighting the game rules to play the role I want to.
I do like how they’ve opened up the species in general. I have a character in a campaign that is essentially based on my cat, a tabaxi rogue with impulse control issues.