As you say, 'standby' should not be an issue, particularly for 'modern appliances'. However, as I recently wrote, one cannot (should not) expect to continuously run items of equipment without their consuming a modicum of electricity - in my house, I have things like routers, extenders, network switches, time switches, aerial amplifiers, smoke/heat/CO alarms, clock radios etc. all running 24/7 - and, at night, IRs, intruder alarms
I have 10 electronic TRV heads, each uses 2 x AA batteries, which last a year or more. There is no need for items to use a large amount of power, but clearly there are the exceptions.
The Sky+ box (not tested, new box) had to power the LNB to know when there have been changes in program times, so this used a far bit on stand-by, seem to remember around 15 watts.
Mains powered zigbee devices act as a relay, not measured the socket adaptor, but if I want the TRV head to link with the hub, and be able to turn on central heating when wife's bedroom get cold at night, it needs to be powered up. And the two TP-Link hubs, Kasa and Tapo again need to be powered up if the doorbell is going to work.
The whole idea of the hubs, is that the wifi router uses more power to the hubs, and they allow things like the TRV heads to run over a year on a set of batteries.
But some items today really don't need a stand-by mode, the whole idea of a TV on stand-by was the valves were kept warm, or it took 5 minutes to heat up when turned on, but TV's don't use valves any more. So, even with a stand-by mode, there is no need for it to use massive amounts of power.
The light switches from TP-Link (Tapo) use a pair of AAA cells to work the electronics, again they last a year. My test was around the tails into the CU, so thinks could switch on/off while testing, so not accurate, but turning off the lights RCBO reduced power by 0.04 amps, so 9.2 watts, which makes me think there was a light on somewhere. But turning them back on, there was an increase of 0.11 amps, 25.3 watts, where some smart lamps auto turn on after a power cut.
But 192 to 629 watts used overnight, it says I have used 4.2 kWh today, (11:30 am) I have boiled a kettle, my fermenter is sitting on a demo under floor heating tile, on a thermostat to keep it to 20°C, but can't really explain why I have used that much, and at 8.5p/kWh that's 35.7p so why worry?