It used to be that going to Harvard was largely a measure of whether you had enough money to go to Harvard. In 1950, the acceptance rate at Harvard from elite preparatory schools was almost 90%.

Today, it's an "egalitarian meritocracy." The acceptance rate is around 5-6%. A quarter of students come from families that make below $80k, and 60% of students receive some financial aid. In other words, a household income of $80k, which is top 30% nationwide, puts you at the bottom 25% mark at Harvard. Further, 40% of students apparently come from households making over $180k (the point at which aid phases out), which puts them in the top 5% or so of households nationwide. The statistics at Princeton, Stanford, etc, aren't any different.

People in the start-up world talk about "egalitarian meritocracy" in the same breath as they say they give explicit preference to kids coming out of Stanford, a place where the median person is from the upper middle class. It's true in a purely relative sense. It's very meritocratic compared to how things were historically, and how things still are in many parts of the world.

That is not to say that these institutions could be appreciably more meritocratic by their own efforts. Rather, when talking about whether a field is "meritocratic" you can't ignore the fact that class and income-based sorting takes place at a much earlier stage in the pipeline.