Accepting failure

I just had an interesting conversation with some other members of my course team, in which I argued this case:

If we decide to move to new content, when we know that nearly 50% of our students haven't mastered the current content, then we are de facto acknowledging that this content wasn't particularly important, and we should not have taught it in the first place.

I hope to flesh out this argument in more depth, when I get a chance, but I wanted to get it down while I'm thinking of it.