That is exactly right. "Good" only matters at all if everybody can agree on what "good" is and not just now, but for all time. And then, assuming you could get everyone to agree on the definition of "good", you have to define what "good enough" means. This is an impossible thing to do without a standard.
It's like a guy at the front door of a nightclub saying, "Hey man, I know we have a long line here, but you can get into the club if you have enough units", and then he walks away.
Everybody likes to try use their own experience, their own wisdom to determine what "good" is and then construct an ideologyaround that. It keeps you from having to face the possibility that there is a higher authority that has to be ultimately answered to, which is quite uncomfortable when you start to think deeply about it.
And I also completely reject the commonly-used example of "there are so many non-Christians that are better than Christians, in terms of their character and behavior. Does the idea ever occur that maybe the "Christians" aren't really Christians? Going to church and saying, "I'm a Christian" doesn't make one a Christian.