TL;DR:

Geothermal energy is currently only feasible in very few places where heat comes close to the surface. We are limited by how far we can dig.

The article doesn’t really go into detail on how, but basically it’s due to pressure and heat, drill bits last less time the deeper we go, eventually there’s just way too much pressure.

But lasers don’t have this problem, enabling us to dig much much deeper, potentially making geothermal practical in many more locations.