Are they? Anecdotally, I'm in St. Louis and Houston regularly and every mall I know of in both cities has always been busy every time I've been to it in the past five years. The more upscale malls in Houston are actually so busy that I can't bear to go more than once or twice a year, and I'll usually take Uber when I do because parking is so congested and difficult. Granted, these are both relatively large cities, so perhaps that's a factor here.
No, but that's a point that a certain type of person likes to push. As this article [1] starts, "maybe it's that reporters don't like malls". You could add "and Hacker News commenters" after "reporters" there.
Yes, but for every Galleria or Woodlands Mall there's a number of malls like Greenspoint or Northwest, losing anchor stores and becoming very low quality. Even malls like Deerbrook, which while still containing mainstream stores and staying pretty busy, are very obviously becoming run down.
Well, to be fair, Greenspoint (also affectionately called "Gunspoint") is not exactly a thriving area. I don't think it's surprising that a mall in a run-down area might be run-down.
It wasn't always that way - it was originally intended to be a thriving area (see the office buildings in the area), but during development, the economy went sideways.
As the linked article says, it does vary with higher-end malls tending to be in better shape. This matches my personal experience. One local mall that counts a Penney's and a Sears among its primary anchors doesn't seem to be in great shape. But if I go into Boston, something like Copley Place seems to do just fine. The shopping malls across the border in NH also seem to be regularly packed but that's something of a special situation because of sales tax.
Also, I've seen B&N stores in malls before.