String theory at least predicts gravity in three dimensions. Other approaches to quantum gravity are not even far enough along to do that - it was an immense and relatively recent accomplishment to have LQG on a circle.
“Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory--an event which would have refuted the theory.”
- Popper
You're welcome to set the bar of meaningful at any level you like; such a statement cannot in principle be disagreed with. However the point stands that string theory has made more accurate empirical predictions than any other theory of quantum gravity. That doesn't mean no other theory of quantum gravity will ever beat it, just that the focus on string theory among people and funders who are precomitted to studying quantum gravity is rational.
Put another way, so far string theory is an elaborate kind of curve-fitting — a mathematical construction that matched the empirical data available at its inception, but one that to this day has never predicted a novel measurement. Unencumbered by the theory, we would not have expected any recent experiment to produce different results.
And yes, that's what I meant by LQG being a less mature theoretical space. Either LQG will fail to find a solution for 3D space (so sad), or it will and its solution will make falsifiable predictions that are not part of existing theory (yay!), or it will propose a set of solutions that make no new falsifiable predictions (in which case it enters the same state as string theory). Both of those first two possibilities would be forward progress.
In book "Everything is Now" by Bill Spence writes that research in string theory led to developing new mathematics which led to helping to manage data in hadron collider which led to detecting Higgs boson. It is not direct cause and effect correlation but it helped with due process.
For example, astrology probably developed techniques of recording astronomical events and likely some mathematical techniques, but that does not mean that astrology is a correct theory.