You could ask yourself though does all "dialog" carry equal worth? personally I would say that "what is art" is a question that has been dwelt on far too much, maybe worthy of discussion but thaty discussion has been drawn out for decades because it provides cheap media attension and justification for carrying on creating a certain kind of work who's merits are otherwise questionable.
Beyond that I think the question also becomes who is art having a dialog with and to what end? a small group of very wealthy/educated people making very on the nose social/political points to each other via art is something I can see many questioning the worth of. Personally I think the dismissal of romanticism/pictorialism is the dismissal of much of human nature, removing much of the emotional response to art in favour of purely intellectualising it. Meanwhile other forms such as photography and cinema that haven't done this have taken its place as the art forms that have cultural relevance.
I wouldn't relate impressionism or even some post impressionism directly to modern art personally, I mean the former took some time to be accepted but not THAT long and by the time of Picasso and Dali those artists were very significant cultural figures in their lifetimes. Within modern art I don't think nearly the same is true, you maybe have someone like Banksy but I think he's very atypical in style where as many of the most praised modern artists are totally unknown to 99% of the public.