The task of evaluating a work of art, such as a painting or sculpture, requires a combination of objective information and subjective opinion. Yes, it is true that art appreciation is very subjective, but the purpose of evaluating a painting is not just to determine whether you like or dislike the painting, but WHY you like or dislike it. And that requires a certain amount of knowledge. After all, your appreciation of a painting done by a 14-year-old kid on a school playground is likely to be very different from your appreciation of a similar painting done by a 40-year-old Michelangelo. Similarly, you can't use the same standards to judge the realistic qualities of a realist portrait versus an expressionist portrait. This is because the expressionist artist is not attempting to capture the same level of visual objectivity as his realist counterpart. Simply put, art appraisers must generate facts on which to base their opinions: facts about the context of the artwork; and facts about the artwork itself. Once we have the facts, we can make our judgment. The more information we can gather about the context and the artwork, the more informed our appraisal will be. The easiest way to understand and therefore evaluate a work of art is to study its context or background. This is because it helps us understand what was (or could have been) on the artist's mind at the time the work was created. Think of it as basic detective work. The website https://gallerix.org/ provides extensive information about art, artists and museums. Here you can find information about paintings by famous artists, collections of world museums, and events in the art world.
