I know it's not entertaining because I turned it off after the result had been sealed for a while. I don't watch Champions League because the result is almost always given beforehand.
You know it's not entertaining because you're not watching?
I think it's the other way around; you're not watching because you know - or think you know - that it won't be entertaining.
Agree with the last bit, though; no such thing as an entertaining football match.