The watchOS 11 update turns your Apple Watch into a proper Apple TV remote. Even if you don't plan on using this feature, you should set it up in case you lose or break your Apple TV's physical remote control.
New remote control functionality is facilitated through the Apple Watch's Remote app. The app itself isn't new, but it's been updated with the functionality that it should've had several years ago. If you've ever used Remote on an iPhone or iPad, you should be familiar with the Apple Watch's newfound capabilities—you can finally control your Apple TV's volume and power from your wrist. There are also some advanced settings, such as audio captions, tucked behind a three-dot menu in the Remote app. (For those wondering, navigation controls were already available in the Apple Watch Remote app.)
After installing the watchOS 11 update on your Apple Watch, open its Remote app and select your Apple TV (both devices must be on the same Wi-Fi network during setup). Your Apple Watch will display a passcode. Enter the passcode on your Apple TV, and you're good to go. The Remote app provides a ton of touchscreen-based controls, though you can also spin or press the Digital Crown on your Watch to adjust volume or call upon Siri.
Note that the Apple Watch's Now Playing app offers some exclusive Apple TV controls, such as a "skip forward 30 seconds" button. I suggest using both the Remote and Now Playing apps for a more robust experience.
The watchOS 11 update is available for the Apple Watch Series 6 and subsequent Apple Watch models. An Apple TV update is not required for Remote control functionality, though discontinued Apple TV models tend to be a bit flakey when it comes to Remote functionality.
Source: Apple