That was a very interesting watch! Wrt why music doesn't contain great melody anymore, I lean to the facts we are bombarded with music without melody, people tend to like what they hear frequently, most people are followers, and capitalism drives artists to create more of the same; The vicious circle of supply and demand. Will it change over time? Likely. Will melody become great again? Possibly. When? Well, it may take a bit of time, maybe even some decades, or even several generations.
Melody is one aspect of music, albeit a big one. I think this is a case of other aspects such as sounds being emphasized.
Modern popular music is simplified to a very large degree. The question is whether folk music was ever more sophisticated or not.