You might be surprised at the depth of knowledge your average Farrier has about both horses and blacksmithing. They might not have a degree in metallurgy, but you can bet they understand the crystalline structures of iron, and how to use that to their advantage. You can also bet on them knowing more about the hooves and related structures of a horse much better than your average vet.

The problem with your hypothetical worker is a lack of depth into any one topic. If they're half artist and half front-end developer and half back-end developer, of course they're not going to be able to get into great depth on any one topic.

I firmly believe in the value of such a Jack-of-all-trades, but I'd be silly to not value the full time artist who can create better works in a third of the time, because they understand their tools and their craft.