My framing for this is "mass production of stimuli." Before industrialization, the number of things grabbing your attention at any given moment wasn't super high. But once you had mass production, and especially the innovation of extrinsic advertising (associating psychological properties not intrinsic to the product being advertised itself), we were all suddenly awash in stimulating signals. But like this article notes, those stimuli go mostly unfulfilled by the action we take (buying the thing, opening the app), and so we all have this low level background noise of frustration and dissatisfaction.

EDIT: Some later posts mentioned it, but philosophers and religions have contemplated this stuff for centuries. Nevertheless I do think it's an exacerbated problem in the modern world due to technology and scale.