Great rant, Justin!
...I only disagree with this:
So, where’s your heat going if you’ve got a brand-spankin new ride today? Right out the tailpipe is my guess.
Your guess is wrong. A more efficient burn means less energy is converted to heat. While exhaust gasses will always be hot, other than Toyota's heat-recovery system found on 2010-and-later hybrids, you're correct with all of your other points about why smaller/aluminium engines simply produce less heat.
The oddball, IMO, is my 2010 Corolla CE. I drive the same route to the gym every morning. By the time I've driven 1.7km, I have lots of heat (with the fan-speed on 3 or 4, which is far too loud), but I can turn it down to 1 after another half a km. If I leave 'Rolla to idle in the driveway, it'll take ~15mins before it heats up sufficiently.
I'm surprised to hear that the Impreza didn't warm up even while driving for a bit. Our Forester (albeit a piggish XT with the 4-speed auto) is warm 'relatively' immediately. As is the RX400h, with its now aged 3.3L V6. Not sure if the 2006 hybrid has any sort of electric heating, but to my understanding, it does not.