Why is contemporary painting no so good like the old paintings done by the likes of Michael Angello, Rafael, Leonardo Davinci?

Art needs to be clear and understandable not only to the other artistic minds but also to the layman.

Paintings by older artists were clearly understood by everyone. There were no certain rules to be followed to portray their individual style of art. An art does not need to follow any rule to bring out its naturality. But when one follows rules it looks too artificial and monotonous and looses its vigour and vitality.