I do not have a complete understanding of bitcoin, but I feel that the PoW concept will not do it in the long run, so I need you to explain to me if I'm wrong.

1. First of all, all this work force is crazy, one day it is possible that it is totally unprofitable for mining and the only able to lead is a very large society, so that decentralization Is broken (I feel we are close to this situation)
2. It is a significant waste of energy, can we sustain this in the long term.
3. Does anyone look for another way to create a block? I've heard about proof of stake, but I'm also not convinced (I think it's worse in terms of centralization)

Thank you