They're beautiful, but years ago I was on a white water river rafting trip and the guide knocked down any human generated rock art he would find.
The reason he said is it was hubris to insert your ego into other people's experience of nature. It distracted from what was already beautiful and transcendent.
I'm not exactly sure I fully agree with him, but when I go to the beach and see these installations, I do tend to see them as intrusions, rather than art.