You cannot totally disable Google TV on a Chromecast with Google TV device.
But, there is an "Apps Only" mode that simplifies what you see and hides recomendations.
thank for your replies. The answers don't help me a lot. In fact, to be more precise, I would like to disable / erase netflix application. The goal is to cast netflix from my smartphone and not using the app on the google TV (as the CC V3).
Doing it, It is no need to enter my account on the CC
I'm sorry for the late response. You can try to uninstall the Netflix app on Google TV and cast content from your phone to the TV. Also, please be advised that you can still use your Chromecast with Google TV just like a regular Chromecast and cast content from your phone even if the apps are installed on it. Check out this support article to learn more.