As I (very roughly) comprehend it, those who understand all that IP number and port management magic available in better routers are able to block or limit unwanted traffic to a specific device. For instance, they wouldn't let a tv send info TO Samsung, only receive. Pi-hole does that for ad servers, but for privacy and security we probably need more granular control of the data packets coming & going. There are programs like Wireshark that let you sniff your network traffic --but I don't know how to use it.