The argument that "genetics in D&D don't work like genetics in real life" is like saying "physics in D&D don't work like physics in real life," except they do. Presumably, a spark and kindling produce fire, fire and water produce steam, and steam and a teakettle produce a whistling that tells the British it's time for biscuits.
Certain expectations from the real world carry over into the game, and they inform and ground gameplay.
The implication of the D&D rules is that yes, genetics do work like real life, which is why half-elves and half-dragons and aasimar and tieflings and sorcerer bloodlines exist. The racial change is arbitrary and amounts to "a wizard did it" for explanation, which rightly rankles those who enjoy a marginally more cohesive fantasy world, those who enjoy the design aspect of racial ability scores, and those who enjoy keeping D&D's traditions alive.
It's not a dealbreaker for me, but sweeping discontent under the rug with "it's fantasy, it doesn't have to work like real life" is quite dismissive.
For those dissatisfied with the changes, I can only encourage you to take the chassis of D&D and customize it for your home games. Remove, alter, and add elements according to your preference. It's how Runequest started.