I don't think that biological advantages (claws, scales, wings, gills) are what is being argued as being racist. An aarakorca can fly, a tabaxi can climb, a triton can breathe water, an elf can see in the dark and a dwarf is less affected by poison. No one is saying biological advantage is bad.
But how do you balance them in a game?
Is flying worth the same as seeing in the dark or resisting poison? Is breathing water equal to a breath weapon? What does a human, from which all modifications like poison resistance is measured against, get when they don't have any biological advantages? Are we okay with the idea that humans or halflings have no inherent biological advantages compared to flying or the like.
So the issue becomes how you balance those biological advantages without relying on stereotyping cultural or mental abilities?