It is a wasting because it could be done with staking, that way the could shouldn't need miners. And i think this is why ETH is moving to PoS.
And it's a waste if the energy cost is bigger than the mined coins...
Sometimes it's just a waste of energy because the thing is the amount of bitcoin that they are mined was just bigger than the electricity bill of the used energy by the bitcoin mining so I say that somehow it is just a waste of energy because there are a lot of kilowatts that is used by but not suitable enough for the bitcoin mining so it is kind of wasting some of our energy especially right now that the electricity supply was not enough to sustain all the needs of the people.
I feel like it also depends on the rigs used by the miners. I read back in the days that people can use ASIC miner rather than using their usual GPU for mining Bitcoin. In terms of consumption energy, I am not sure if in the future we could make renewable energy to power up these mining so that it could at least lessen the usage of electricity, because in some countries that becomes the barrier for people to mine cryptos.