Ethernet doesn't use TCP/IP. Ethernet is it's own network. It has nothing to do with TCP/IP.

Other things use Ethernet. Routers, when connected to each other, often use a local Ethernet network to communicate.

Think of the TCP/IP Internet as it's own network, ignoring how routers physically talk to each other. Sometimes it's a directly link, a wire. Sometimes it's carrier pigeons. Sometimes it's WiFi. Sometimes it's Ethernet. Whatever it is, it's local to between the routers and does not extend outside that.