Canada

Appeal to authority argument incoming. Points to self. Am scientist. Am geoscientist. Am hard rock geoscientist who professionally uses instruments to quantify rock properties.

You're quoting things that do not apply uniformly across the shield as though they apply across the shield. Nuclear waste storage locations ideally are within granite plutons, of which there are many within the shield. You don't think the people looking to develop storage facilities don't look for the most competent rocks? There was a research facility in Pinawa Manitoba for years -- they mapped every fracture in that rock from above and below. They learned construction techniques tailored for the rock. It's goddamned perfect.

Furthermore, have you ever heard of grout? How do you think hydroelectric reservoirs retain their water when built in the shield? Engineering and materials science are marvelous things.