I am old enough to remember when string theory was expected to explain and unify all forces and predict everything. Sadly, it failed to deliver on that promise.

And there is no known single real world experiment that can rule out string theory while keeping general relativity and quantum mechanics intact.

More accurately, string theory is not wrong (because it just cannot be wrong). Because it does not predict anything and cannot invalidate anything, it does not help to advance our understanding of how to integrate general relativity and quantum mechanics.

It should not be called theory - maybe set of mathematical tools or whatever.