It would be...I agree. But I don’t see any harm in showing kids how to do that problem the traditional way...and somewhere in the 4th or 5th grade teachers can show the CC way...and they should be able to identify the kids who appreciate the better method.
Something I failed to mention in my prior post also - a lot of grade school teachers really aren’t that good at math. And many aren’t ready to learn a new style of doing math. So for many of these teachers, they go through the CC math in a mechanical way...but aren’t good at ‘teaching’ it. The only solution is to wait until today’s kids become teachers. And IMHO, all the more reason to wade into this pool more slowly, and let the kids who are self directed learn it with or without a good teacher.
While I understand your point, I have to counter by asking if you are sure your opinion at this time might be just a bit of atavisim? The idea behind teaching everyone the new method is to give them a new way of approaching numbers; a way that we only learned through either inference by experience, or just stepping away from anything beyond arithmetics.
I understand the old way "works," but the new curricula makes the transition from arithmetics to algebra utterly seamless. And if there is one thing I have noticed about our society in general, we just don't have the mathematical acumen to think of "using what we know to find out what we don't" as an integrated thought process.