2W idle isn't low-power?

It requires active cooling doesn't it...

I've had good luck with entirely passive cooling for a pi5. It was 12 bucks for a the osb cnc aluminum version. https://www.digikey.com/en/blog/edatecs-two-fan-less-cnc-cas...

Pi 4, depending on the environment, also needed active cooling, in my experience. Especially in summer, with room temperature above 28*C, it couldn't handle any load until I added a fan. (The good thing about it was that I could control the fan with PWM easily - it was fun :))

But the Pi 3 didn't. You'd think with the process improvements they'll be able to have more performance in the same heat envelope, but they want to do their own Pentium IV...

Process improvements can only go that far - register banks, speculative execution, instruction reordering, many execution units and so on use power, but are needed because the processor can be faster, but the memory is still much slower.

I'd agree except the laptop i'm typing this on seems to use 4.5 W right now, the whole system :)

I don't expect Apple like power/performance ratio from everyone, but they could at least try...

No, it does not.

The Pi500, which is essentially the same hardware, works with passive cooling.

Active coolers exist to fit within the tiny footprint. If you have the space, you can go with passive cooling or a cooling case (essentially a large heatsink).