@Appelmoesje okay so what you're thinking about is the aesthetics and beauty of art. You like the classical and skillful from what I got. Even those had meanings. The statues you were talking about? Setting beauty standards and morals for anyone walking by them and also painting heros in the most perfect light making them seem above human.
The thing with as you call it "modern art" or the better word would be "dadaism" is challenging what art even is. After the invention of the camera and photography people didn't see why they should continue taking so much time for so much detail in art. So they started doing what cameras yet had to achieve, color. That's why the first abstract pieces in history are super colorful and play with multiple perspectives in the same object. Perfect example for this is Paul Cézanne. After this art evolved a lot and quickly. People tried capturing different things, feelings even, e.g. expressionism. Art mostly evolved from art and anything that inspired, inspires and will inspire