It's not that it's duplicating a spell, it is a better version of a Warlock invocation. That's too good for a racial ability. And it is on top of two skill proficiencies and a strong recharge-on-short rest combat defensive ability.

Between social encounters, skill versatility, and combat there is not an area of the game where the Changeling race does not provide a very strong boost to strength. It is unbalanced relative to other strong options in the game. They gave it too much.