My own personal philosophy is that a good group or at least a good game master will be able to make sure that everyone has fun with all but the worst of systems. That being said, that isn't a far cry from the settings trump mechanic philophy.
For me, one of the most telling arguments about the power of settings is that there are dozens, if not hundreds, of books that are set in the Forgotten Realms, Dragonlance's Krynn and Ravenloft. And I have to believe that a lot of the people who buy and read those books don't actually play in those settings. If people who have no investment in the mechanics like the settings, that says something.
One of the two campaigns that I was in that lasted for over a decade ended up going through five different sets of mechanics. Obviously, the story was more important than what we use the dice for.
Mind you, my personal example works at least as well for the argument that the group itself determines how good a game is. And mechanics are important. They define how you interact with the setting.
But I do see how settings can be the hook to grab players and how they help define the stories that you will tell.