Harvard’s freshman class is more than one-third legacy ... legacies were five times more likely to get into the world-famous university than applicants without relatives who went to Harvard. https://www.cnbc.com/2019/04/07/harvards-freshman-class-is-more-than-one-third-legacy.html
That's really doesn't indicate that those admits are morons. Obviously they got a leg up from having parents who attended, but a lot of that leg up was the best schools and best experiences and best upbringing; not fair but also not the same as admitting morons because they have rich parents. Which at least in the case of one of the schools listed (not Harvard) I know isn't even remotely possible because the coursework would kill them. Of course not for nothing the Harvard application does ask if your parents are alumni and my school did not, so I won't defend legacy admissions at Harvard too much.
There was a New York Times article about Harvard admissions about 20 years ago. The source said that they could admit a whole class, put that aside, admit a whole second class, put that aside, admit a third class and that third class would be just as qualified as the first class. There is a significant amount of randomness in being admitted into Harvard if you are qualified. Legacy eliminates that randomness. If you are the direct descendent of John Harvard, that level of legacy will likely eliminate the “qualified” part.