And the most important thing(s) that any experienced HA automation geek knows is:
1) Always have a manual way to control a device if HA goes down.
2) Local only, no cloud.
It is for this reason that my lights (Hue) and switches (Inovelli) are bound in ZigBee groups. HA adds some niceties, but the lights still work if it’s down. Accent lights I have bound to the Hue Bridge, because their app adds features HA doesn’t have, and they aren’t required for emergency egress.
The only gap I have, I think, is that because I’ve set all bulbs to respond to power restoration after a cut in last known state, if everything somehow lost its Zigbee binding, putting switches into dumb mode locally still wouldn’t help. However, since that’s an improbable scenario, I accept the remote possibility in exchange for not being awakened from lights coming on in the middle of the night. Plus I keep flashlights / headlamps throughout the house.
For a home, I'd argue that you should fail open, for safety. So now I'm sleeping or out of the country and the software fails and the doors unlock.
Then there's the quality of the software. Home Assistance is probably fairly good, but the software in the devices probably isn't. All the demonstrations I've seen of home automation, regardless of supposed quality and interoperability has been, in my mind, yanking as all hell. If an IoT sensor reports nothing, is that because there's nothing to report, or has it lost connection, or is the configuration broken? I'd be constantly nervous about the later two. A practical example is tire pressure sensors, I despise them. They are more often than not misreporting, so you learn to ignore them.
And as you say: "any experienced HA automation geek knows", yeah, but I don't want to be a home automation geek, I just want the stuff to work. I don't want to be bothered by setup and configuration, I don't want to think about it, ever.