Midnight, I agree with you to a great extent, even though I do teach CW!
I think you can teach it - just as painting, singing and sculpture can be taught.
But just as with these arts, the person needs to have talent to begin with (you can't "put" it there) and needs to have realistic expectations.
What do I mean by this? Well, I have had people on my courses who have never written anything longer than a short story before, and yet expect to learn the craft of novel-writing to professional level in a year or two. It can be a lifetime's craft. I was sending stuff off to publishers for 6 years before I got a sniff from any of them, and that's seen as pretty short.
Nobody joins a beginners' art group expecting to exhibit in the Tate, and nobody takes up the violin from scratch expecting to be playing in the LSO in two years. And yet people expect the equivalent - professional publication by a major publisher - to happen with writing.
And I also agree to a great extent about the "young writers" thing, even though I was 23 when first professionally published. Those writers over 30 do, generally, have more interesting things to say. I can't help myself checking the author biogs in bookshops these days - if they were born after 1980 I put it down!
Interestingly the average age of writers on the NYT Bestseller List a couple of years ago was mid-50s. It's still a craft/job in which you are expected to be producing your best work in your late middle age. Thankfully!