I have no evidence other than my ideas but the decline of malls feels to coincide with the rise of the internet. A lot of the generic malls perhaps did not innovate on their business, they relied on big brands to lease out spaces in the mall, big brand food names to run spots in the food court and beyond maintaining the space, they did nothing to improve their circumstances. Before the rise of the internet it was an easy way to go an entertain your kids or yourself for a few hours, even if you did not buy anything. Now people entertain themselves with phones and enjoy shopping online.