I've unfortunately been in the position of your boss in the past. In some of my early product management/project management roles, I would wave my hands write a few emails, one-pagers and expect the developers and designers would grok the vision and build something beautiful. Surprisingly, in my first experience, the outcome was wonderful -- the product was beautiful. At that time, I was naive and vainglorious enough to believe that the reasons for it were my 'vision'. The actual reason was a team of world class ux designers, visual designers and developers, who understood what I needed and created the product. The creative vision was theirs. So in some sense your boss is right, he doesn't have a unicorn team who can translate his day dreams into product.
On the other hand he is also profoundly wrong. Skip a few years, and I started up on my own, and could no longer afford those unicorn designers and developers. Now mere vision was no longer sufficient, I had to deal with actually firing up Photoshop and Illustrator and going from there all the way to writing HTML/CSS/JS, even the backend python for a prototype (Fortunately, I've always loved coding.) The learning was profound. Translating vision(even your own, leave alone others') into attractive product is a difficult skill that every serious product owner must understand. And they can only do so by doing (they may never master it). I'm not anywhere as good as those unicorn UX/devs I worked with in the past, but I compensate for it somewhat with, meticulous communication, verbal discussions, wireframes, mocks, sketches, functional prototypes, whatever, to get the product I want. Then I iterate the hell out of it by getting feedback. Learning to interpret subtle signs of friction in a users' experience was hugely valuable. The results have been good though slow.
If your boss is refusing to acquire the requisite translation skills, you will need to acquire them (and you will probably be the gainer in the bargain)
My advice to you here is to do the following:
1. Ignore the public shaming, if possible, and focus on your boss's message. Iterate on design concept despite his demeaning you for mistakes. It may eventually make you the unicorn developer/designer. At the very least even if you realize you don't have a talent for design, you will understand where your own limits lie.
2. Understand that the kind of people your boss is looking for do exist. They are not easily found, and are usually very expensive. So help your boss find one if possible. Learn from these people.
3. When you've gotten these skills, please email me your resume. :-) (Just kidding)