I was only loosely familiar with string theory. There was no class in grad school for it, but it was discussed on occasion (usually outside of the classroom). I didn't know any professors working on it.

From what I gathered at the time, they constructed an idea, and the did the math. The math seemed to give them the answer they were looking for. On the surface, I'm OK with that. It was decades before GR could be verified after the math had been worked out (there were some earlier tests, but the "clincher" wasn't until 1954 en.wikipedia.org - Tests of general relativity). But that is the trick...it could -in principle- be verified when Einstein first proposed it (he even proposed the tests). String theory has never suggested a mode to test it.

If it can't be falsified, it isn't useful. Whether "string theory" or a deity, doesn't matter.