Of course you can set up firewalls and VLANs to have the best of both worlds. You can remotely interact with an IoT device like this to set them off or check the status, but the device itself can't see anything else on the local network.
I have all of my IoT devices on separate Wifi network(s) and VLANs and almost all of them are isolated so they can't talk to each other, plus I occasionally look at how much data they are sending/receiving from the Internet (some is expected obviously, and it differs by device).
Doing this requires a considerable amount of admin work and IT knowledge though. It also requires something a step above most consumer grade or supplier provided networking equipment.
I've never spotted anything egregious like the coffee maker in the OP but if I did I'd be making sure other people knew about it and the device itself is either firewalled off properly or replaced by a brand that isn't a security risk.
I have all of my IoT devices on separate Wifi network(s) and VLANs and almost all of them are isolated so they can't talk to each other, plus I occasionally look at how much data they are sending/receiving from the Internet (some is expected obviously, and it differs by device).
Doing this requires a considerable amount of admin work and IT knowledge though. It also requires something a step above most consumer grade or supplier provided networking equipment.
I've never spotted anything egregious like the coffee maker in the OP but if I did I'd be making sure other people knew about it and the device itself is either firewalled off properly or replaced by a brand that isn't a security risk.