Bitcoin mining is not a waste of energy because of this bitcoin mining we will be able to mine bitcoin and make a supply of for all the world and this is a way of earning money so I can say that it is not a way of wasting energy, perhaps those people who are saying that it is just a way of wasting energy is just like nothing happens but in bitcoin mining people are earning by doing this.
You don't get the actual topic man, the thing is how POS is better than POW and since POS is already a good algorithm why do need need to waste energy to mine POW coins since POS is a simple solution and I do agree that POS has upper hand because no matter what but energy and resources are being wasted in POW indeed.
it could end up making Bitcoin centralized. Think about it. Imagine being a huge exchange with a lot of PoS coins in custody? Solely from being a whale, you automatically have a significant influence over the network. In contrast to PoW whereas you'd actually have to dedicate money to buy hardware.
But, to buy those hardware you need to invest money and like you said if someone grabs a big number of coins they can control the network similarly if someone has a lot of coins they can sell off buy miners and actually be a whale too.