the trouble with perfection

By the end of the High Renaissance, young artists experienced a crisis: it seemed that everything that could be achieved was already achieved. No more difficulties, technical or otherwise, remained to be solved. The detailed knowledge of anatomy, light, physiognomy and the way in which humans register emotion in expression and gesture, the innovative use of the human form in figurative composition, the use of the subtle gradation of tone, all had reached near perfection. The young artists needed to find a new goal, and they sought new approaches. At this point Mannerism started to emerge. The new style developed between 1510 and 1520 either in Florence, or in Rome, or in both cities simultaneously.

Source: https://en.wikipedia.org/wiki/Mannerism