@matrix I think the turning point was the First World War, not the second. The First World War had a devastating and destabilizing effect on Europe in which the sense of continuity was broken and it left many western men, especially the post-war elite perplexed, pessimistic, disoriented, and disillusioned of their civilization. The Second World War only accelerated this trend.
@Proton
I think the better argument is simply that the art work selected for each period is cherry picked. That said, I do myself prefer older artwork than new when it comes to paintings.
@matrix