> What would have been an impressive final-year project when I was in university is something high schoolers are churning out as a bare minimum. How do we ready our kids (who are competitive) for this if not by ensuring that they don't miss out any opprtunities?

This sounds US-centric, looking from the outside it appears that you tried so hard to not use tests and marks to rate students that you made it all about projects/volunteering which mostly benefit kids with a lot money and time support from parents. It very much looks like performative kabuki for admissions officers where teenagers have lost interest in building something for the sake of it.

Anywhere else in the world, bar the US and the rest of the Commonwealth, it is all about grades and having exams with normal distributions as the great equalizer. For all the pros and cons at least anything else you do in your spare time as a teen you do it without any external agenda. A 16 year old shouldn't be worried about how something will look like on their CV.