The time has finally come for geothermal energy

I've always been curious why a cost-effective widespread implementation of geothermal energy has never been considered a holy grail of energy production, at least not in the public debate. Much of the discussion is so focussed on nuclear fusion, which seems so much harder and less likely to be reliable.

Why not is explained in David McKay's book Sustainable Energy - without the hot air

https://www.withouthotair.com/c16/page_96.shtml

The problems are that rock isn't a good conductor of heat, so once you've cooled a bit down, you have to wait for it to warm up. Warming only happens very slowly at the rate of < 50mW / m² which limits the amount of power you can get out.

Couldn't you frac the rock like they do with oil and gas drilling or have a branching borehole?