And I recently remember hearing forced air is bad for air quality inside! Did I hear wrong or is there something more to the story like “forced air brings in outside air, so if your outside air is bad you’ll have trouble”?
Modern systems (since late 80s, maybe?) have return air ducts so that you get even heating even if interior doors (e.g. bedroom doors) are closed, but older systems may only have one return vent per floor or even just a single one in the house, and depend on gaps under doors and such for return air circulation.
Bigger commercial forced-air systems have had exterior air intakes and heat exchanger systems for a while, but are pretty new for residential (I've never seen one in the wild myself).
I lived in a house built around 1985 that had one, which was R-2000 [3], so they're at least that old.
[1] https://en.m.wikipedia.org/wiki/Heat_recovery_ventilation
[2] https://www.nrcan.gc.ca/energy/efficiency/housing/new-homes/...