Even from a lefty perspective: people vary wildly in the value they produce. A society that paid based on output would be as if not more unequal than today's. Plus it does nothing for the people who need money to live but can't or don't do economic production: children, elderly, disabled, caregivers, etc. Socialists will sometimes emphasize the share of productivity captured by capital to argue for redistribution to labor as a class, but for individuals to be paid their own productivity is AFAICT not any serious movement's demand.

And then obviously from the capitalist perspective, your employment only exists to the extent that the employer derives more value from your work than they pay you.