What exactly do they mean by wastage of energy? Energy is wasted only when nothing is gained from them. Generated Energy from Solar, Wind, Water and other renewable means is used in the form of providing entertainment and to fulfill our basic needs. You pay for the electricity you use and it is being used in some form or the other. Renewable resources are always replaced and would never likely end. On an average, it would cost around $3000 - $5000 to mine one bitcoin. If the miner sell them, they would get a profit of around 1.5x - 2x they have spent in the form of electricity and at the current trading price of 1 Btc.

The energy consumed by the ASIC's are used for generating money and for securing the decentralized payment system all around the world. Miners doesn't waste the energy rather they use these energy to generate money. Wasting is something which is used carelessly or for no purpose to anyone.

When mining is being done, the ASIC's generate a lot of heat. This heat energy can be re-used and can be converted into an energy. Intense Heat Generated form these ASIC's can be used for many practical applications. I have even read somewhere in the past that, Denmark and Germany paid it's citizens to use their electricity as they were high on renewable electricity production.

PoS and other energy efficient mining process apart from PoW are created to reduce the usage of energy in the process of mining the blocks. This would make the miners take little to no efforts in mining apart from staking coins. Mining a #1000 block and #100000 block will literally have the same difficulty. Some algorithms similar to PoS will favour old miners and whales rather than a miner having the potential and equipment to mine the block. This also makes some to stop trading and use their coins for staking to earn profits.