If no one is willing to spend the money to seriously build a new mall then the mall is dead. It will still be part of the landscape for a while, just as you can see the remains of failed fast food chains, nuclear weapon launch sites, and pre-bussing decentralized high schools, but that is just reuse.
Lots of places in the world malls are still being built at a rapid pace. London, for example, is seeing an ongoing stream of enlargment, redevelopment and new mall developments. For an example local to me, the Australian developer/mall operator Westfields has formed a joint venture with another developer to combine two local malls and redevelop them into one huge mall, which make Westfields 3rd huge mall in London:
Maybe large parts of the US just has too many/too large ones, given how many of them were developed pre-online shopping. And a problem with malls is of course that population shifts are far harder to accommodate when such a large area is operated as one unit. If the mall owner does not actively manage changes due to changes in the surrounding area, it can easily become obsolete as a whole.
If no one is willing to spend the money to seriously build a new mall then the mall is dead. It will still be part of the landscape for a while, just as you can see the remains of failed fast food chains, nuclear weapon launch sites, and pre-bussing decentralized high schools, but that is just reuse.