This is an interesting perspective but if Bitcoin were to take over the global economy, the deflationary nature of Bitcoin would discourage people from spending. So it would not need to process as much value as the current inflationary financial system which relentlessly stimulates consumption. Also, when the block rewards end, miners will only earn from transaction fees so mining will be less profitable so miners will consume a lot less energy.

All that said, I do think that Bitcoin uses too much energy currently and far more efficient blockchains exist and deserve more attention.