Your thermostat should does not need an internet connection to measure temperature and turn on the furnace. Indeed, an oldschool thermostat with a mercury switch can do that. No mater how awesome your "smart" product is, it needs to not fail it's primary function unless its physically broken.

I'm also looking at Alexa and the stupid plug someone got me for a gift. Sure, I use it "Alex turn on the lamp" but I know that the system is totally unnecessarily dependent on the internet and two distinct companies for that to work. I would never have purchased such nonsense for myself.

People in tech have strange ideas about what it means for something to work acceptably.