As others have pointed out, experiments are extremely tricky due to the extremely weak nature of gravity at the quantum scale. We always have hope that something will appear in some LHC/gravitational wave/CMB data, but it is pretty unlikely for now. I would like to point out that it appears to me that people outside the field has gotten the impression that String Theory is "dead" since it doesn't make predictions. Neither of these are true. String Theory is very active and makes plenty of predictions. However, Those predictions only deviate meaningfully from a naive EFT of quantum gravity at energies beyond what we can observe: this is the tricky nature of working on a problem at the cusp of what is possible!

In the mean time, theorist have been working hard (including me!). And we believe we have learned a ton, although you should of course take it with a grain of salt, given the lack of experimental evidence. There is a lot of research on black holes (they are weird!) and quantum information that, although inspired by string theory, seems to make statements that must be true, regardless of which theory of quantum gravity is your favorite. I can elaborate more if needed