I wouldn't be so quick to judge. It's pure research, and String Theory has pioneered a lot of new ideas that have successfully cross-pollinated into other fields. Even the LHC employs String Theorists with good reason.

Seems a mistake to write it off as "not delivering" simply because it hasn't given us exactly what we originally expected.

On a more social level, a focus on "delivering" and "impact" in pure science seems like it can be taken to the point of shooting ourselves in the foot. Think of all the discoveries from pure exploratory research that we recognized as useful only after the fact.