I have to be careful here because lots of folks on this forum think I'm a raving liberal and others think I'm a radical conservative, and it is because of what I think about issues like this that confuses folks.
What I think, Darrin, is that the abdication is an unintended consequence of people honestly trying very hard to bring more equal educational opportunities to more and more kids at younger and younger ages. And I think that that is a worthy objective for our society. Having said that, however, I think that some genuinely mis-guided principles became driving forces throughout the curricula of education - training programs (by this I mean the curricula that went in to teaching college-aged kids how to become teachers).
I think that at least one if not two generations of teachers were produced that were/are hard-working, well-intentioned, and mis-guided. I believe that they reflected the community values that said "Let my children be exposed to whatever everybody else's children are exposed to, whether they are ready for it or not", and simultaneously "let's make sure that no child's educational experience is a negative one because I don't know how to handle a kid who can't keep up". Remember that I am saying that the teachers are reflecting community values; the teachers are not creating the values.
Societally, we Americans fail miserably at passing on our own civilization to the next generation. We don't teach people to be parents, so we look to schools to parent for us. Then we don't want schools doing anything "to our children" that is the "prerogative" of parents. The result is that our kids grow up in a "least common denominator" milieu where going along with the most popular issues on television or mass media is what passes for learning society's norms.
My son started school in the early 80's (I'm very old), and I went to the local public school to see what they were offering. I asked the principal, "How do you handle values?", and his answer was that "We don't." He didn't even realize that his answer was a value statement.
My kid went to a religious private school. And he went to a rigorous high school and college. I was willing to pay for what I knew I wanted to help me in how I raised my child. But most Americans don't know, or don't even think about, what they want their child to learn. And our schools are doing the best they can. It is not good enough, though.