This is the exact reason I don't really like cloud connected IoT devices. For instance, while I'd love to have a Nest thermostat, I refuse to us it due to requiring a connection to function fully. So I've opted instead for a 'dumb' thermostat with WiFi and an open and well-documented local API. About the only current exception to that in my house is my Amazon Echo, and that will be replaced as soon as someone comes out with a viable local-only alternative.
Yeah, I agree. I will always give preference for devices that fully function without internet access. For instance, the Venstar thermostat I use has a cloud component where you can track stats and remote control the device if you want, but it's 100% optional and the device loses no functionality, beyond the on-device weather, when there is no internet access. The local APIs allow me to easily integrate it with my HA controllers as well.