One of the worst things that has happened as a result of the failure of string theory unification is that many people have interpreted this as a failure of the whole idea of using mathematics in fundamental physics. The failure of string theory has nothing to do with the sophisticated mathematics involved, the problem is that string theory unification is just a bad physical idea that doesn’t work.
There are many possible places to look for inspiration for new progress in fundamental physics, with mathematics just one of them. Physics has traditionally made progress mainly through experiment, but we are at a time in history where we are hitting limits on our ability to explore experimentally new territory at high energy. Serious work on understanding the mathematical structures behind the incredibly successful Standard Model may be a much more difficult way to make progress, but it may be one of the few viable options we have still open.