The artist in question actually has some skill as a painter:

As I've seen many times with technically skilled painters though, movement, composition and fluidity are a struggle.  On a very high level, it's the difference between Frazetta and Boris.  Boris is every bit as proficient with the brush as Frazetta was,  but a lot is lost when it comes to bringing "life" to his paintings.

I'm unfamiliar with Evans other than a quick Google search (http://www.vinceevansart.com/)  but I'd bet that as good as he paints, he's learned that the gift of making a comic book character look natural isn't as easy as it might seem.  

In general, I think most people don't truly understand and appreciate just how much goes into being a good/great comic book artist.