It's quite inefficient, but Bitcoin energy usage isn't something that can just be fixed or that outweighs the benefits of it. It's not like using electricity is an
inherent cause of climate change, it's just a
current cause of climate change. There is plenty of energy to be used, particularly nuclear energy, which by the way is safe
compared to coal and oil.
Solar and wind power
are unreliable, but solar for example is useful in the daytime when there is the most usage, and over time there may be breakthroughs in battery technology which affect how we view these things.
Regardless, the current banking system is not particularly efficient anyway - although to be fair, if Bitcoin was more popular it would use much more electricity than banking does now.
