String theorists are bullshitty yes.

Mathematicians aren't - you can prove their correctness over abstract planes and use them to for example run a hedge fund or a software company into trillions of revenue when making testable predictions in macro reality.

Theoretical physicists that use mathematics to make testable predictions are too. You can use them to also make electric engines, statistical extractors and accurate physical simulations that are corroborated with empirical evidence.

If the prediction is not testable, is unfalsifiable, is unreproducible, is not independent and is not supported by overwhelming evidence - it is bullshit - no ifs, buts or ands.