Recently one of my Zigbee-controlled thermostats started pumping cold air constantly. To fix it, all I had to do was open and examine the board; one of the varistors got some battery acid on it when I had an alkaline battery burst in the unit. Because it was a no-name with an actual PCB, I was able to solder a new varistor in place, and it works good as new.

So I would say that "Smart Local Control" isn't the problem, but rather the ability to repair the thing. Also, the thermostat was $45 when I purchased it 5 years ago, so it was a good investment IMO. I think that's why everyone is upset about the Nest gen 1 and 2 sunsetting; there should be no reason that these devices should be breaking now (no failing electronics) but they die anyway because the company is too cheap to keep an extra endpoint running.

1. That you can buy a smart local control device.

2. That the electronics were designed with appropriate thermal management so they don't fry themselves quickly. Smart bulbs are the most notorious offenders here, but the problem is widespread.