I don’t make much of the C and D percentage at Brown or at any other highly selective college. The grades, standardized tests (well, prior to test-optional), ECs, etc. now required to get into Brown means that the entire student population is pretty much hard-wired to never get a C or D. For all of the legacy and donor tropes, most of those admits earned As in high school, too. Even recruited athletes at a school such as Brown got good grades in high school.
These kids are so well prepared and the competition for selective admissions is so fierce that it’s unrealistic to expect a precipitous grade dropoff in college. To use a concrete STEM example (since everyone seems to think the Ivies only teach gender studies for some reason), why would a student who earned an A in Algebra II, an A in Pre-Calc, an A in Calc I, and an A in Calc II in high school suddenly not be able to grasp Calc III in college? Especially when for many of these kids the aggregate workload (in the classroom, out of the classroom, and with ECs) in college is far less than it was in high school?
Now, there is PLENTY of what I would consider grade inflation going on at the top schools, but it’s in movement from the B into the A range. That’s what I would consider a somewhat artificial piece of the grading trend. But at the selective schools, the disappearance of the “Gentleman’s C” owes more to the reduction in the number of “gentleman” in the Ivies than it does to the grading policies.