There's probably about 1% of the people on BGG that pay enough attention to ratings to be able to separate the two values.
I must disagree on this as there have been several discussions about this issue.
I think that the rating system on the geek is one of the most central functions there are. Together of course with many others.
Plus pretty much everyone attaches a different meaning to the actual number. Something you'd entirely expect in an unmoderating rating system with thousands of contributors.
This you can say is a Bell distribution, meaning that there will always be people who judge games in an off the meanstream values.
Of course will the broad mass give each game a proper rating.
If we entered another rating so we have two ratings. This would give the Geek-world a finer tuned system to judge on different games.
One for game quality (theme, mechanics, quality, etc) and another one for playability (todays scoring ground)