Hmmm. Not sure. Fine arts is strange, and different from other areas of the humanities. In my opinion, for the last 70 years or so, the high-art mainstream has largely rejected technical prowess as a marker of quality or significance (or a sufficient qualification for “insider” status), and so critics and historians fall back on biography, cultural context, education, etc., as a means of comprehending and evaluating art. Though, at the same time, it has elevated certain eccentric outsiders, so it’s not so simple.
I think in other arts, like literature and music for example, a person who has worked outside of the mainstream, or who has developed her skills independent of traditional schools, might be labeled, semi-derisively, an “autodidact,” but since technical aptitude matters so much more in those fields, the proof would be in the pudding, as they say.