The idea expressed in the original post, I think, more rightly refers to the problem of the hack artist. An artist like Thomas Kinkade can find an effective emotionally manipulating technique and then use it to get a specific and predictable reaction from the viewer. But I don't think that is what is effective in art. Good art is an exploration that is begun by the artist and picked up and continued by the audience. Art, like science, should never begin with the answer it is looking for, but instead look at evidence or experiences as the raw material to propel one toward a new or more complex understanding of the world.
The idea that an artist "has something to say" is a bit of a confounding point. My take on this issue is that art is not about saying something. It is about searching and discovering and communicating an experience. If you begin a work of art with the intention of making a specific statement, what you are actually doing is creating propaganda. It might be very nice propaganda, but it isn't going to be a transformative experience for the viewer. Where art can be quite powerful is when the artist is open to new experience and searching for answers they do not already have. If that artist has adequate skill, they may be able to create an image that communicates that discovery to an audience.