Does this mean that a painting has to be beautiful or perfectly executed to be a good work of art? Yes, but that will depend on how you see beauty. I think If a work of art can draw your attention in some way or another it as already fulfilled it's objective. Which is to transmit something to the viewer even if on a very small scale.
Developing an understanding of art is not that difficult at all. It's true that some critics and art lovers devote their entire lives to studying the minutest of details of an artists’ work, and come up with all sorts of explanations of why the artist painted a specific imagery and what he was thinking of. Believe when say that they are not always right about what they are trying to convey or put across. However i can understand such behaviour because what is in fact important is what a painting means to you. It is important to me that a painting transmits something to the viewer, but
that's not always what a work may transmit to me...What I'm trying to say is that there’s no need to be an art expert to have a meaningful relationship with art. All it takes is a moderate attention to detail, a little bit of patience, and a willingness to let it reflect on your own feelings.
Great art can be amazingly rewarding (again this will depend on what to you is "great art") but you can't spend a lifetime pondering on the decisions the artist made in one painting. Instead, you should just take what the painting, sculpture etc...gives you. Andy Warhol once said: "if you want to tell the difference between a good painting from a bad one, all you have to do is to first look at a thousand paintings before". There are no rules whatsoever about what is a great piece of art. In my opinion a great piece of art is what it can transmit to you, if it can indeed transmit something to you, it was all worthed. Remember that Van Gogh’s work was once considered amateurish and forgettable. There are, of course, standards that may matter within the professional art world, but i don’t owe those professionals any-fuckin'-thing, so i don’t worry too much about what they think about my work or what qualifies as “great”, i think you shouldn't to.