>Is the problem that there are lots of mediocre artists but not many who can actually execute projects?

I think part of it is that standards keep increasing. Compare this demon concept art from Warcraft 2 (1995): http://vignette2.wikia.nocookie.net/wowwiki/images/c/cb/Daem... to this one from WoW: Legion (2016): https://s-media-cache-ak0.pinimg.com/736x/56/f2/7f/56f27f98a...

There are probably a lot of artists that can execute at the 1995 level who aren't employable in 2016.

It's just a hard problem, especially when you have to try and get a number of different artists to maintain a single style for a project. Disney was struggling with this problem for decades and financially they were hardly breaking even with their studio part of the business because of the cost of generating all the art they needed. Computers lowered the costs and the manpower quite a bit, but then increased the quality expectations.

There's also the problem of working within technical limitations. Even with standard file formats there can be much more involved than just dumping files into a project.

I would imagine artists need to be involved in technical discussion and would need to learn & bug-test custom software for importing and processing assets. It seems like a different skillset to traditional art & design backgrounds.