String theory has been pretty useful outside of string theory proper. There are analogies to lots of other systems which I think continues to breathe life into the research. See: https://www.quantamagazine.org/string-theorys-strange-second...

> “It’s hard to say really where you should draw the boundary around and say: This is string theory; this is not string theory,” said Douglas Stanford, a physicist at the IAS. “Nobody knows whether to say they’re a string theorist anymore,” said Chris Beem, a mathematical physicist at the University of Oxford. “It’s become very confusing.”

I knew some string people who easily transitioned into other fields (like condensed matter) because the work was similar. I don't personally see it as a huge waste of time, and it's like the least expensive thing to fund.