Its not an indicator of audience perception. Its an indicator of Audience interest though I think we're saying the same thing. Are you saying there is a correlation between the quality of a film and box office? Because a film can be successful and popular but still be of bad quality because it had great marketing.
And it does look at reviews of ordinary people through user reviews. How could it devalue the authenticity of the RT meter? It does its job of rounding up critics reviews and gives an average of how many critics liked or hated a film.
But that's why before I see a film in theaters, I do take in account IMDB too despite that not being 100% accurate due to fans.
Whether people take this as a film being good or bad is in the eye of the beholder, but the RT meter to me is often pretty spot on about a film most of the time.