So the problem comes that D&D race traits were a mix of biological (wings, darkvision, waterbreathing), cultural (proficiencies, languages) and magical (innate spells, fire breath) with a certain wink-and-nod that it didn't matter which was which. With cultural elements no longer being able to be used, we are stuck with magical and biological, and the line between them being blurrier (magic also absorbed some of the cultural traits, like the giff magically having firearm proficiency or elven trance granting tools).
If you were to draw a clear dividing line between biological and magical (or worse, attempt to limit or remove magical) you'd find a very small window of tools to work with. Assuming all species are built as "how they differ from human", you can only have some many "move faster, lift more" style augments or give species so many different climb/swim/fly speeds. And of course, the idea would be that species need to be balanced to be playable: it might make biological sense that a halfling is slower or weaker than a human or goliath, but that don't make them very fun to play.