Salvador Dali used the visual language, not for the sake of it, but to illustrate his psyche, his favorite subject matter. When I visited the Dali exhibition at the Centre Pompidou in Paris in 2013, I could see how people were hooked as they accessed Dali's very unusual mind through his numerous art pieces. They were fascinated by Dali's exceptional mental giftedness, his overflowing delusional paranoia, and the fair amount of death and pornography included in his work. I was myself almost under the spell.
Dali is undeniably an amazing painter, at least technically. In fact, his technical virtuosity is so overwhelming that, at first sight, one may think it is what his paintings are about. The technical qualities of his paintings (smooth finish, pseudo realistic rendering) and the unusual subject matter (projection of the mind, melting watches, organic forms of unclear origin, surrealistic world) are what makes us believe that this is great visual art. But it is masking the reality, which is that Dali’s paintings are actually about the verbal concept of “paranoiac knowledge”, as he called it, or "the ability of the brain to perceive links between things which rationally are not linked", and not about the painting itself. Dali described his work as a "spontaneous method of irrational knowledge based on the critical and systematic objectivity of the associations and interpretations of delirious phenomena." His subject matter is his psyche. His process is based on psychological introspection. One could almost say Dali paints from imagination (as opposed to nature). The painting is just a support to deliver his concepts.
For example, in The persistence of Memory (see picture below, on the left), the notion of hard versus soft, the symbol of the time that passes, and the oniric or delusional imagery refer to verbal concepts issued from Dali's mind. The soft central piece may even be seen as a symbolic representation of the artist's tortured mind, half sleeping or delusional. In that sense, Dali's painting virtuosity takes us where he wants us to go, which is inside his complex mind. For that reason, one could consider him a brilliant, efficient painter.