The only way to win is not to play. It is completely daft to me that all these devices require an Internet connection to function. I will never allow something like that into my house (along with home assistants like Alexa). I have achieved a decent level of automation using simple timer switches (they have ones that adjust on/off times based on your latitude), completely disconnected motion sensing lights, and by si…
HomeKit and ZWave don't require an Internet connection. I use a bunch of ZWave devices connected via Ethernet through a Raspberry Pi with hassio and a ZWave USB adapter - controlled from my phone when it connects to my wifi network.
To protect your wifi network, make sure you have a decent gateway in place. OpenWRT does a great job, but there are many others as well.