In physics there are real tests and relations that have meaning so it makes sense to ask if String Theory is correct or useful. In mathematics there are complex structures built from axioms and sometimes these structures can be related to each other in interesting ways. Will anything important ever come of String Theory? Maybe, but from a mathematical point of view no theory needs to correctly model what is real or have demonstrated application to be worthy of exploration and study.
The particular thing that comes to mind repeatedly when reading this is the fact that more or less all of mathematics can be derived starting either from set theory or from logic theory. There is no particular reason to choose one or the other, but set theory is the most common foundational substrate. Depending on how this is done it may be more simple, easy, or direct to express or make proofs regarding some particular idea or domain. But Wolfram seems to be seeing things in terms of there being a big space with defined paths through it. Instead of leaning on set theory or logic theory to get to a particular expression or result there should be a global basis for expressions and results. That different models can be used for the same phenomena doesn't seem to be considered valuable or even a possibility.