There are caps in place. The earning cap is now $168.6K That is the upper limit for your earnings to be taxed. If you make more than that you only pay in as if you made $168.6K That number goes up every year because of inflation.
There is a maximum social security benefit. It is also a cap. It is $3,832 per month if you retire at full retirement age in 2024. It is different if you retire at different ages between 62 and 70. The number goes up each year because of inflation, and people already receiving benefits get COLA also.
Some people want to remove the cap on earnings at $168K and make folks pay the tax on all their earned income. The sky is the limit. That means that some folks might pay 100 times as much as others, but still get the max benefit of $3.8K/month. That isn't right. It makes social security a welfare plan, as benefits are not based on earnings.
It is no less fair than paying everyone the same benefit, regardless of what they paid in. It just affects a different group of people.