What do you think about this "painting"?

I agree it is nothing more than a blue background with a white line, however in art the value is not of the painting, but what someone is willing to pay for it. For example Barnett Newman was once quoted saying "old standards of beauty were irrelevant, the sublime was all that was appropriate - an experience of enormity which might lift modern humanity out of its torpor" his pictures were a decisive break. Remember that the art market isn't determined by questions of intrinsic value. If you do not like the painting, then that is just how you feel, you are entitled to like or dislike. Art appreciation is subjective either you like it or you don't.