If you use "smart devices" cheap Chinese garbage that requires a 24/7 connection to some random insecure cloud server in your home, you're a fucking moron. But there are some great solutions that run entirely locally and enable you to do some really cool home automation. Check out the !homeautomation community, as well as !homeassistant. Home Assistant is probably the best piece of software for building an actually smart home, that's also sovereign and not reliant on an internet connection or some company and their infrastructure.