My favorite example of why advertising/marketing is important but not overwhelming/unstoppable is in the hit-based industries: If the industry had a "make a superstar" button or a "make a blockbuster movie" button they could just keep mashing, they'd be mashing it constantly. You wouldn't see franchises go from top-of-the-world to decline like Marvel or Fast and Furious. You wouldn't see expensive new bombs or failure-to-launch reboots. There is countless chatter out there about industry plants, organic vs PR-shilling word of mount campaigns, etc. But... if that's all it took, it would be wayyyyy more constant. A lot of words spilled recently about a band, Geese, and how their buzz wasn't as organic as it seemed... for a band that's still, at the end of the day, quite niche and small-in-audience...
It's very hard to get a huge hit without marketing - even great word of mouth benefits from amplification - but it's also near-impossible to force a hit into an audience that isn't vibing with it. The highest-grossing movies, or highest-listened pop music, is a combo of marketing + accurately hitting extremely-common/trendy tastes. See also iPhone marketing vs Windows Phone marketing. I thought Windows Phone was better; none of my friends or coworkers was convinced even after I showed them my phones. The mass media consumer may not have thought much about their tastes or tried very hard to be more adventurous, but that doesn't mean they don't like the stuff they're eating.
I think this is still in many ways bad - at the very least, it's incredibly inefficient to have a billion-dollar zero-sum "pick this one over that one" industry. But I don't think it's a deadly threat. (See also any number of "tons of money and star-power behind them" failed political candidates too...)