Let me begin by saying that I am not at all a painter or a sculptor.
I am mainly a VFX compositor, Film maker and Musician. What I do with visual art is just pixel pushing! Hand me a lick of paint and some brushes for real and I would turn it into a massive mess!
Many Artists however do not see 'digital art' as an art but more as a skill.
And I agree with that... Learning to do a magic trick is a skill but once you move to putting that magic trick or in case of VFX digitally manipulated picture into illustrating a train of thought that triggers or provokes an emotion then to me it has become an art.
Oh and I am also the author of the book