I’d say that depends. Some consumer routers may have guest network and client isolation on it though I doubt most do. Higher end routers support vlans can be configured that way and could be configured in many other wise such as talking to network 1 but not 2 or 3. For instance, I have IOT vlan allowed to connect to my server vlan for DNS since I self host DNS, but my general VLAN for personal trusted devices does can’t be accessed by IOT.