I was surprised at the use of the word "artless" in this context, and had TLIU in order to learn of its possibilities as a complimentary adjective (Having or displaying no guile, cunning, or deceit; Free of artificiality; natural: artless charm.) i was further surprised to find that, at least according to atomica, the definition that i've heretofore ascribed to it (Lacking art, knowledge, or skill; uncultured and ignorant. Poorly made or done; crude.) is listed as a *secondary* meaning.
I like this one! What do you think about this? The opposite senses of 'artless' derive from the two senses of a single definition summed up this way: artless--without aritifice, whether disemblance/facade or [what's a better word for "cultivation?"]. Do you think you've come up with yet another class of polysemic words, Bridge?
