There's a saying that humans only understand three probabilities: 0%, 50%, and 100%. So if 90% of people who are rich were born into wealth and 90% of all people are not wealthy, what does that mean?

Usually the knee-jerk response is to say that it's equally easy for rich and poor to end up wealthy, or sarcastically claim that it's supposedly impossible to become wealthy if you were poor.

Statistically, it'd mean that while 10% of rich people were self-made, they'd only represent 1% of the overall population, meaning it'd be roughly 100 times more likely for someone who wasn't born wealthy to remain poor.

These are gross oversimplifications with numbers that are not based on fact, but it's just a simple example to show that something can be possible in a system where certain people are disadvantaged and it doesn't detract from the fact that systemic issues exist.