I would never make a determination regarding whether the teacher or the students are more at fault in poor exam performances without knowing how much of the reading and homework assignments the students are doing. Teachers cannot and should not shoulder the blame for poor exam performance when students who are not doing the assigned reading and homework exercises score poorly on the exams. I am also not a big fan of AP courses. I've known too many cases where students perform very poorly in downstream courses having managed to get through the AP courses without learning (or perhaps not retaining) very much. I'm not sure what you mean by "quantitative only" methods. Most quantitative homework and exam problems require a lot of qualitative thinking to draw the right picture, identify the right physical principles involved, and assess the reasonableness of the numerical answer and the units. Sure, students may be tempted to approach problems with formula roulette, but it's part of a teacher's job to steer them away from that and to assign questions that do not reward that approach.