I have it on.
For everyone with unreliable FaceID unlocks: enter your passcode. I went ahead a few days ago and used FaceID from weird angles + entered the passcode immediately after failed attempts and now my FaceID is essentially „bulletproof“. Haven‘t had a single failed scan attempt in several days (other than the given ones where you cover up the sensor or take too long to properly align them with your face).
Your FaceID model is updated every time you enter a passcode and it detects similarities (e.g. its your face but the system isn‘t „100% sure“ so it fails).