Just because it's energy dense after enrichment, doesn't mean it has high concentrations within mined ore. Most mines operate with only a fraction of a percentage of the ore being uranium, and only a fraction of a percentage of that is U-235, and viable for a nuclear reactor.
Some mines use ISL techniques which is similar to fracking. Canada does have Cigar Lake, the highest grade uranium mine in the world (15%), but due to the dangers of high uranium concentrations and the challenging geology, it has not been the easiest to extract.
This is to say, you don't just dig up some ore and stuff it in a reactor(it takes a lot of ore to power a reactor), nor is uranium mining a clean process.
