I never said that someone's income quantile was dispositive. If my parents never took the SAT and have no idea what it is, I'm at a huge disadvantage to do well on the test by any measure. Regardless of their income. Again, the SAT isn't testing for academic aptitude but for the cultural knowledge of parents and peers.
As a wealthy parent I know exactly how to throw money at prepping for one test: hire expensive tutors and purchase practice tests. Gaming years of GPA or coming up with a compelling story is more complicated and difficult to solve with the application of financial resources.
A system with vague and subjective criteria is subject to bias, for sure. They are also more difficult to manipulate directly with wealth (other than bribes). We have to decide what our priorities are there as a society.
And you’re missing the point re: income, which is that all poor kids aren’t similarly situated. Asian kids raised in the bottom 20% of the income scale have a 25% chance of ending up in the top 20% as adults. For white kids it’s only 11%. Socioeconomic status is a factor but it’s not dispositive or insurmountable.
As to grades—you think it’s easier for a bright but poor kid to do their homework in time for 12 years than to study for one test? As to “personal stories”—that’s just a vector for manipulation by the whites people who run the admissions system. It’s remarkable to me to read anecdotes from admissions counselors, who say stuff like that they are looking for weird and non-conforming kids: https://www.cnbc.com/2021/10/22/former-stanford-admissions-o.... Talk about cultural loading!