For reference, shipping containers make sense for root cellar/storm shelter type underground storage – you can just dig a...
For reference, shipping containers make sense for root cellar/storm shelter type underground storage – you can just dig a trench, drop them in, cover it up, the earth will provide insulation and you won’t be tempted to cut windows in the load-bearing walls. They do not make sense as any other kind of inhabited structure. They are an enclosed, stackable space, yes, but any of the many further modifications they require for habitability work directly against that, in most cases even if you like the industrial look of corrugated metal it would be more efficient to build with standard construction methods and apply that as cladding.
Also, malls basically in no way have electrical, plumbing, insulation, or layout suitable to residential conversion, are very expensive to keep climate-controlled, and boomed in the postwar off of a sped-up depreciation schedule for tax deductions that encouraged them to be developed quickly at the cost of high operating expenses and little incentive for survivability after two decades.
Ditto those really really big commercial skyscrapers.
The little ones yes worth rebuilding the entire interior, big ones no.
One non-obvious thing is that the flagship of postwar commercial skyscraper design (it’s striking how Sears Tower has fallen out of memory along with all of Chicago), the World Trade Center “twin towers”, was destroyed after 28 years, preempting any questions of long-term viability.