To be fair, we've locked ourselves into this to some extent with the focus on lithography and general processors. Because of the 10-1000W bounds of a consumer power supply, there's little point to building a chip that falls outside this range. Peak speed sells, power saving doesn't. Data center processors tend to be clocked a bit lower than desktops for just this reason - but not too much lower, because they share a software ecosystem. Could we build chips that draw microwatts and run at megahertz speeds? Sure, probably, but they wouldn't be very useful to the things that people actually do with chips. So imo the difficulty with matching the brain on efficiency isn't so much that we can't do it as that nobody wants it. (Yet!)
edit: Another major contributing factor is that so far, chips are more bottlenecked on production than operation. Almost any female human can produce more humans using onboard technology. Comparatively, first-rate chips can be made in like three buildings in the entire world and they each cost billions to equip. If we wanted to build a brain with photolithography, we'd need to rent out TSMC for a lot longer than nine months. That results in a much bigger focus on peak performance. We have to go "high" because we cannot practically go "wide".
edit: Another major contributing factor is that so far, chips are more bottlenecked on production than operation. Almost any female human can produce more humans using onboard technology. Comparatively, first-rate chips can be made in like three buildings in the entire world and they each cost billions to equip. If we wanted to build a brain with photolithography, we'd need to rent out TSMC for a lot longer than nine months. That results in a much bigger focus on peak performance. We have to go "high" because we cannot practically go "wide".