Half the blame goes to the batteries
These modern batteries are simply amazing in they retain voltage to the last hour or so. What I mean is.. if you look at battery discharge graphs, the end looks like a cliff. The result is, it's unlikely we'll see a device, that runs on those batteries, self detecting the end, for that price point.
If I get any message at all about a low battery, it's that it's at 50% and if you (again) look at a graph, that's minutes from zero. (Zero being 2.8 v which is where the circuitry quits working.) Hard to send a "battery's dead" message when the battery is... dead.
But your major point, I think, is the consumption. 21 days.
I had something similar during my transition. With multiple systems hammering my 60+ devices, battery life was grim. I do have a lot of Aeotec product here.. Recessed door, mini, nano and wall motes, micro and nano switches, and MultiSensor6's. Once I got everything over and the other Hubs shutdown, battery life went back to normal, although it seems Aeon is less long lasting than their competitors.
But never, ever... can't say I'm ready to agree to that.