The issue with traditional logic solvers ('good old-fashioned AI') is that the search space is extremely large, or even infinite.

Logic solvers are useful, but not tractable as a general way to approach mathematics.

> Logic solvers are useful, but not tractable as a general way to approach mathematics.

To be clear, there are explicitly computationally tractable fragments of existing logics, but they're more-or-less uninteresting by definition: they often look like very simple taxonomies (i.e. purely implicational) or like a variety of "modal" and/or "multi-modal" constructions over simpler logics.

Of course it would be nice to explicitly tease out and write down the "computationally tractable" general logical reasoning that some existing style of proof is implicitly relying on (AIUI this kind of inquiry would generally be comprised under "synthetic mathematics", trying to find simple treatments in axiom- and rule-of-inference style for existing complex theories) but that's also difficult.