I think it's worth quoting the video's main thesis, "if the creations of great artists reveal psychological and spiritual atmosphere of the times, then an honest survey of modern art must lead one to consider the possibility that modern civilization is suffering from a spiritual sickness".
I think the creator of the video is interpreting historical artistic changes with a highly shallow perspective, i.e. psycho-spiritual.
The video's creator states that "prior to the 19th century, the great artists focused on works that beautified the world and transfigured the human being," but this is true only at a cursory glance across art history. First however, it needs to be said that much of the famous Renaissance and Baroque artwork that the video's creator describes were commissioned by the church or
wealthy individuals, so it is understandable why so much artwork in this time depicted a famous biblical scene or a idealized individual or "transfigured human being", etc. The market was dominated by money.
But of course, his statement is not unequivocally true. Take, for example, Pieter Bruegel's
The Triumph of Death? Or the
panel of Hell within Hieronymus Bosch's Garden of Earthly Delights? Grünewald's
Isenheim Altarpiece, while religious, has one of the most sickly-looking depictions of Jesus in art. What about Caravaggio's
The Beheading of Saint John, depicting a religious event (the beheading of Saint John the Baptist) in a strikingly irreligious and brutally insignificant manner? There are numerous examples of course, showing the shallowness of his thesis.
There is in fact a lot of questionable material and analysis in this video, and I'm not sure how much I care to analyze a Youtube video essay, but I don't see any issue with humanity or religion being de-focused from art, nor do I see it as de facto evidence of cultural decline, as if Mark Rothko, Fernand Léger, or Jackson Pollack and many others could possible be offering that suggestion in their artwork. Seems like the video creator is just glib about modern art, as are many people, unfortunately.