When you "don't understand art," a not entirely irrelevant question is how a piece of art that is a strong reminder of what your three-year-old does in kindergarten can be worth millions at auction. The same goes for modern art, where a straight line on a white sheet can be sold for similar amounts.
It is of course easy to think that a well painted, purely technical and well made cardboard should be expensive. However, it is not particularly difficult to copy a motif or to paint it and make it look natural.
Because many people can paint well, it is more and more difficult to communicate something with their art, to underline certain aspects, to communicate in a more subtle way and to allow the recipient to look at the subject from the artist's point of view.
Really good art succeeds in drawing new frontiers, in experimenting and seeing how far one can go in a way that reaches the consumer but also forces them to re-evaluate themselves and see the world in a new way. It may also take a certain level of maturity in one's examination of art to appreciate these subtleties and appreciate the new way of thinking.
The more you look at art, the more nuances you see in it, and you also see when an artist is only making art that is easy to digest and relatively substantive. The more you are involved, the clearer your tastes will be.
For example, an artist who paints an abstract painting that looks like a rag may want to do anything that is blurred to illuminate another, more important aspect of the design. You keep what is interesting and make the rest meaningless. So there is a conscious thought behind the "garment" and it follows that the artist can repeat it over and over again.
The difficult thing is not to copy or paint, the difficult thing is to make something new, interesting and to succeed in passing it on.
Abstract art can, once again, be likened to innovative music or film. Punk was perceived by many as the sound of people who could hardly be considered musicians when this style of music came along. Today, however, it is an established cultural expression that is appreciated by many but still rejected by many others. The music is as much appreciated by punk fans as it is by a well-trained opera singer who is appreciated by others.