Someone posted a more informed comment on Hacker News about 2 months ago. The idea is that if you drill to 5 km deep, let's say, you find very hot rock. But once you extract the heat from that rock, new heat is very slow to come because rock is a good thermal insulator. So, you'd need to produce secondary holes. Lots of them. In the end the math just doesn't work out by orders of magnitude.
Someone posted a more informed comment on Hacker News about 2 months ago. The idea is that if you drill to 5 km deep, let's say, you find very hot rock. But once you extract the heat from that rock, new heat is very slow to come because rock is a good thermal insulator. So, you'd need to produce secondary holes. Lots of them. In the end the math just doesn't work out by orders of magnitude.