preface: I took AB and not BC but I feel both are similar in nature.
By bad course, I mean that I feel as though Calculus AB/BC sets students up for 'failure,'
for starters, how successful are BC students in the future multivariable course?
To get a 5 in BC, one needs to pass with almost a 60% of questions correct on the exam. The exam is also all computation (which to be fair is much of Calculus II anyway), but because a lot of the exam is computations, proofs are magically handwaved or ignored in favor of computation (which gives students a bad impression of what math really is). For example, delta-epsilon is never touched on and so when I first encountered delta-epsilon, I was very confused.