If you don't want to have access to FaceTime, simply Sign Out from FaceTime.
- Open the FaceTime app
- Select Preferences
- Click Sign Out
Then nobody can FaceTime you, nor you can FaceTime to anyone without logging in to the app again.
If you just want to disable some apps, create another user account without administrative privileges and then apply Screen Time restrictions to that account.
Likewise if there are multiple users sharing the Mac, create at least one user account per person and then you can apply unique restriction profiles for the respective user accounts.