Unfortunately it’s not that simple–that was kind of what I was getting at.
The router manufacturers don’t make this as easy as it really should be; they all do it different.
Here’s the gist, that might be useful or at least can help guide some Googling:
The basic approach would be to set up two separate networks, with two separate Wi-Fi names. One network is for your trusted good stuff, such as your PC and your iPad. The other network is for “stuff you don’t trust at all”
You only use the “goodguys” wifi network for trusted devices.
You use the “sketchy” wifi network for appliances, thermostats, TVs, printers, and such.
You then configure firewall rules so that “goodguys” devices can see each other and can speak with “sketchy” devices, but only if the trusted device initiates the conversation.
You also set up firewall rules so that “sketchy” devices cannot see anything in your home; they can only speak to the Internet. IF a “goodguys” device starts the conversation, that’s OK. That’s how you would print from your PC to your printer, for example. That’s also how you could screencast from your iPad to your TV.
“sketchy” devices cannot even see each other. This means that some rogue device with malware off of Aliexpress won’t be able to do mayhem with other things on your network.
A different topic, the concept of VLANs, is more about wired networks, but it is kind of like having “sketchy” traffic separated from “goodguys” traffic for plugged-in devices.
This can get as complicated as you want too–a good addition is to have a “guest” network that is similar to the “sketchy” network, but you give that password out to friends.
In a better world this would all be handled with minimal effort by appliances, routers, and so forth; unfortunately, it is up to the family computer geek to sort out the settings for these kinds of things. For example, I use Ubiquiti gear, so I have to know how to configure these things using their tools. It would be entirely different if I were using Linksys or Netgear equipment.