Humans are actually very powerful when you give them the extra feat at 1st level. But most classes like Wizard, Sorcerer, Barbarian need 3 good ability scores to be stong at high levels and 1 mediorce ability score so you can sacrifice 2 ability scores. So having +6 stats doesnt really do that much for a class overall because 2-3 of those ability score increases do nothing for you at all or not enough to matter at later levels. Varient humam in same aspect getting a +1 to 2 key ability scores and a feat of there choice as well as skill of there choice is tooled to customize to any class and spec making them more useful in overall. I mean at level 1 having duel wielding / great weapon fighting or shadow touched for example and starting the game with a 1st and 2nd level spell would basically make you strong enough to off set any other class option from a flavor perspective and free you up to take more ability score increases later as well. Which is basically +2 +2 to 2 ability scores of your choice basically. which makes varient human stronger than most races.
