I'm not sure about the last couple of decades, but prior to that geothermal was usually really a research project. Yeah, it was expensive, but boondoggle is the wrong framing.
OTOH, some of the recent proposals look serious. I'm not in a position to judge them, but maybe they're good. However they are still limited in the sites where they can operate. I'm not sure the ones that involve fracking are both safe and reasonable. And the closed circulation one that I've seen described is really still experimental. Once they get the bugs worked out of it, it may be a really good system, usable in a lot of places. My guess, though, is give it another 20 years before major investment.