There definitely are lower-powered options; I mostly meant that as an example that as an hobbyist, an ESP32 - possibly even on a standard dev board! - could easily be good enough for your use case.

I never did a formal study to see how much of that power use was standby vs. power-on usage, how much of the standby usage was the ESP32 vs. the board/voltage regulators/pulldowns, how much of the power on usage was radio vs. e.g. all the crypto (we're doing asymmetric crypto for the TLS handshakes on batteries here, that isn't going to be cheap!) etc.

I just slapped it together and found it good enough to not care further.

nRF52832 are famous for their low energy usage, it's hard to compete with them. However, ESP32 is much more universal.

No, it was an undocumented one-off using a random cheap devboard from Aliexpress (i.e. not some specifically optimized circuit!), built (IIRC) using the Arduino IDE - aside from spending the time to find and configure the low power mode properly, this was done in the dumbest, most naive way possible, and still worked.