This is only a problem if the computational power is sitting idle, or if there's reason to believe more efficient servers exist and are not being used effective

This is only a problem if the computational power is sitting idle, or if there's reason to believe more efficient servers exist and are not being used effectively. Of course replacing millions of functioning servers just to reduce energy usage is very wasteful in terms of environmental impact too. Lots of that computational power is also used to offset other energy consuming tasks. Like video conferencing instead of office buildings or travel. It's not clear that even 5% going to servers is an issue in that framing. What matters is the value created per person using online services.