I've heard that; I'm skeptical:

First, a favorite hobby to bring down the experts that make you feel inferior by saying there is no difference. 'My kid could paint abstract art.' You see I am not inferior in my understanding and maybe capacity; no, it's all a lie. It's kind of like sour grapes - very convenient to one's ego. (It also a way to shut oneself off from learning and seeing the most beautiful, valuable things in the world.)

Second, when people find one study that confirms what they want (red wine is good for you!), it becomes among the highest impact research in history.

Third, in domains where I have expertise, I can tell the difference when people without expertise insist there is none. In domains where I lacked expertise then gained it, I saw my perception change. I was blind but now I see.

Fourth, in art particularly, including in music, it is the emotional and unconcious that matter most. Those are the mediums where art mostly operates and the differences between mundane, good, and extraordinary usually are not in great strokes but in the smallest nuances. Lots of people can paint sunflowers; the details of Van Gogh's brush strokes are transformative. Like in business: the first 90% takes 10% of the time; the next 9.9999% takes 90% of the time, and the last 0.0001% takes 1,000% of the time.