Opening the YT app should open YT (not YT TV) - thats expected normal behavior.
This also includes YouTube buttons on remotes - opening the YT app (not YT TV) is expected behavior.
If you dont have the YT TV app, you can launch YT TV from within the YT app (click on the YouTube TV link at the lower left in the UI menu).
You didnt mention your make/model/firmware version for your TV (Settings/System/About) or the YT app version (highlight press Options (*) on the remote).
Regardless, try these known solutions/workarounds for YT app not loading:
1) Change your Theme to the Roku Default (Settings/Theme/Restore default theme) - try again
2) Change your Screensaver to a Roku clock (Settings/Theme/Screensavers) - try again
3) Check for updates (Settings/System/System updates/Check now) - try again
4) Remove YT app, RESTART ROKU (Settings/System/System restart), Add YT app - try again
5) Network connection reset (Settings/System/Advanced system settings) - try again
6) Completely unplug power from Roku for 10-15 minutes - try again
7) Factory reset (Settings/System/Advanced system settings) <--- last resort