But at least I would expect the homework done completely at home could be individualized.

Unless your child is in private school, this is way too high an expectation. You really would have done X(number of students) lesson plans ?

So okay, I'm looking for a diplomatically-worded way to say "can my kid please be challenged more?"

Again, good luck on this in public school. With mine, I found ways outside of school to challenge them and they each needed it different ways. Even with some private schools years, I felt fortunate to get each of them finished through high school without major incidents(and I am not kidding).