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.
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.