To be clear, art is whatever. I can't really say "this isn't artistic!" about something because that kind of defies the point. Some things are art to some people and a load of shit to other people.
That being said, I dislike nude art for a variety of reasons. My biggest problems with nude art are the sexism and humanism that are so ingrained in its history. I can't really speak on sexism in the nude art of ancient Greece because it is a bit less clear. However, during the Renaissance and the Age of Enlightenment the intentions of nude art were blatantly sexist. I don't want to write a novel, but here is the down-low. Nude art reinforced gender roles and ideas about female beauty. This really becomes clear once you read up on mind-dualism and sexism. I know, the two sound totally unrelated, but the connection is there. I would recommend reading Bordeau's theory about mind-body dualism being sexist if want to understand this better. The idea is that everything about women is related to the body and physical things. Women are supposed to be beautiful, sensual, fallible, corruptible, etc. Nude art from those times portrays women in this light. This idea really shines through when you consider the religious and philosophical views of the time, which were strongly influenced by mind-body dualism. Women are supposed to look pretty, and we are supposed to marvel at this beauty portrayed in nude art. Leave the "thinking" to the men.
As for modern nude art, it is pretty much the same story without the mind-body dualism. Nude art almost always reinforces societal notions of what women are supposed to be: playthings for men. Sure, we can obscure this fact by calling it art, but the intentions are clear. Women are something to be oogled over.
Lastly, I cannot stand the humanism in nude art. The idea that we should marvel at the sight of a human body is ludicrous to me. It elevates humans to place that they should never be. Humanist attitude has led to countless atrocities and grievances not only against nonhuman life, but to other humans too! The humanistic man knows he is better than the rest, and he is supposed to use his better judgment for the good of society, regardless of what other "common men" might think. Essentially, the intelligent elite know all. Rather than seeing the human body as simply an occurrence of nature, nude art encourages us to place it on a pedestal. Yes, the human body is amazing, but nude art does not show that. You are only seeing the skin-deep persona that you more or less see every day. To me at least, the real beauty of the human body is in the mechanics. This is why nude art does not impress those who are not infatuated with the human body. If the body is shown "naturally", we would not think much of it. Who calls nude pictures from a disposable camera art? The body must be elevated in order to impress people. If you are not fooled by the elevation, then of course nude art is boring.
Now these ideas are not meant to be taken as absolutes. Think of them as trends. There are always exceptions, and correlation does not prove causality. I apologize if this is a bit confusing and drawn out. My mind is scattered at the moment, and I am sure I left important stuff out. Please point that shit out to me so I can explain further.