The high frequency ranges suggested for 5G seems useless, they'll barely be able to penetrate windows.
Increased coverage would be far more helpful than faster speed in most countries.
But suppose I wasn't a neoluddite and I was easily excited by digital salt shakers. As it stands, all of these products could be using wifi, which would still give me, the consumer, the ability to firewall them. That would let me access them on my LAN without letting them talk on the internet. The idea of putting 5G radios in them instead of wifi radios seems to be to deprive me, the consumer, of the opportunity to firewall them.
If you want an automatically adjusting fridge, that can and should be implemented without the cell radio too. Put a RFID chips in food packaging that requests a particular temperature; the fridge then sets itself to the lowest temperature requested. A fridge that instead broadcasts the contents of your fridge to some corporation that does not have your best interests at heart is an abomination, but I do not doubt that whichever corporation starts selling them will try to mask this by framing their spy devices as ecologically friendly to make it seem morally unassailable.
[1] I have to also say generally, as some of the MVNOs do tend to lower data prices over time. There are some bargains to be had there, just with lower network prioritization.
As it is, there are some cheaper options as well (eg, consumer cellular or other MVNOs).