Intelligence isn’t static nor is it destiny.
Or else we wouldn’t have the plethora of accounts of intellectually dim offspring of aristocrats/royalty and the upper classes doing their utmost to restrict access to educational opportunities in order to protect their own progeny from competition from their intellectually superior and harder working counterparts from the “lower orders” ranging from attempts by wealthy Ivy/peer private elite alums attempting to stop the move towards a more academically meritocratic admissions process in the early '60s to wealthy rural Prussian/German aristocratic families successfully doing their utmost to maintain admission process to the military academy system which favored the aristocracy and blocked reforms which would undermine them(i.e. Instituting the attaining of the Abitur as the minimal educational requirement for aspiring German commissioned officers)*.
- In some ways, the Prussian aristocratic junker elite...especially the rural ones are analogous to our modern-day developmental legacies given substantial admission discounts mainly because of their family's high SES status/fame/connections.
What you’re thinking of are average-excellent legacies who get little, if any meaningful boost from the fact their parents/grandparents attended because they didn’t donate large sums to the alma mater or didn’t have the level of achievements, fame, or connections.
The legacies who do get a boost are the ones who donate large sums and have high levels of achievements, fame, and/or connections…and can and do get admitted with mediocre for that given school’s stats.
Most of the HS classmates admitted to Princeton in my graduating class were from this group and the older college classmate who was admitted to an Ivy as a legacy was also a legacy of this type due to his grandparent’s high-level of achievements and substantial donations(think millions to the Ivy alma mater).
The former…likely the vast majority of legacies on this board and in general aren’t the same and do not get the same boost/degree of influence as those from the latter group.