Is it ever acceptable for your kid to bring home an F on a test?
No, it's never acceptable. That it happens sometimes doesn't mean it's acceptable. When you start accepting mediocrity, that's exactly what you'll get. I'm not really surprised that you're the one arguing this point, though.
Ok so when you say it is unacceptable, that doesnt mean you wont accept it, you are saying you do accept it happened but it isnt something that should be the accepted norm moving forward.
Gotcha. That word means both things.
'Sir, your fridge will be delivered next week'
'That is unacceptable, it was promised tomorrow'
'Ok, we were behind but will make sure it delivers tomorrow'
I agree that mediocrity shouldnt be accepted. I disagree with how so many here seem to judge whether mediocrity exists or not at the micro level. A large body of work should be judged as a large body of work.