I think many of these are inherently poweruser features though. Most non tech-savvy people will rarely have to turn off their phone or clear their open apps (really if the memory eviction system is good this shouldn't even be a concern).
Some of the other stuff you mentioned is discoverable in my opinion. Swiping down
from home gives you a search bar. Notifications being accessible by swiping down from the left is admittedly not as good as swiping down from the top bar in the older iPhones, but I think still more discoverable than the Windows notification system that requires you to click a button.
I think you grossly overestimate the percentage of candidates at lower tier schools who would be qualified to pass a Jane Street (or really any HFT firm) interview. Even at the top schools the pass rate is incredibly low. In expectation you would be getting probably <5% of your new graduate/intern class from the entire bottom 80% of schools.
The quality level drops off very sharply after you go below the top 20-30 CS schools. It's just a matter of limited resources for recruiting. The common path taken by people who go to "lesser" schools is to grind really hard to get into a good MS or PhD program and then go to these firms.
Some of the other stuff you mentioned is discoverable in my opinion. Swiping down from home gives you a search bar. Notifications being accessible by swiping down from the left is admittedly not as good as swiping down from the top bar in the older iPhones, but I think still more discoverable than the Windows notification system that requires you to click a button.