The meritocracy only exists at the broad market level. Within almost every organization there is a zero-sum game of mostly politics. The vast majority of Americans go to work in a zero-sum environment. It could be a job waiting tables, it's unlikely to scale with how good you are at it. Or it could be a middle management position. You might be able to play politics for a higher salary, but you aren't going to get it by actually being good at your job. Similarly you aren't going to lose your job by being bad at it, only by being politically inept.
It's setup this way because that's how mid-to-late career employees want it to be setup. People would rather find a niche and then coast than constantly worrying about being outperformed by people younger or smarter than them. If there's not competition, then there's no way for hard work to yield more than slacking off.