In the pre-Internet entertainment business, access to the public was everything. There were a handful of gatekeepers who decided what songs people would hear and which movies they would see. If you couldn't get your project through one of those doors, it was unlikely anyone beyond your friends and family would ever experience your art.
Today, not only is it possible to get your music and films in front of millions of people, but the public is actually determining which artistic endeavors succeed. As a result, quality is beginning to prevail over marketing clout.
It used to be that a mass marketing campaign could keep a bad film in theaters for weeks, and millions of uninformed viewers would continue to show up. Critics were mostly perceived as arrogant semi-insiders and no one really paid much attention to their opinions, if they read them at all. Even if Roger Ebert hated a movie, you would probably still go see it if the trailer looked good. (In fact, you might go out of your way to see it if you generally disagreed with Roger Ebert's opinions.)
Today, there is instant feedback from thousands - even millions - of people within hours of a film's release. These are people like you, including your friends. Their opinions are freely given and presumably unbiased. They have inherent credibility and if they don't like the film, you probably won't either. As a result, the public response can now kill a film within hours, so film makers are more pressed than ever to make films that people will actually like.
It's not that film makers never cared about quality before, but "good enough" used to be a workable standard. Now, more often than not, it actually has to be "good" in order to be successful. And "good" is determined by the actual audience rather than a handful of elite insiders.
Does this mean that marketing is no longer important? Hardly. It is more important than ever. In an environment where the choices are essentially infinite, good marketing is the only way to rise above the din. But once your marketing gets the attention of an audience, your product better deliver or it will a die a swift commercial death.
THX has a famous slogan, "The Audience Is Listening." Well now the audience isn't only listening; they're talking too. To each other. And if they decide they don't like your movie, everyone they know is going to find out really fast.
I think that's a good thing. It makes all of us in the industry pay more attention to what our audience really wants, and that's good business.