I don't know how you could possibly say that. Around the time of BD's release, the Billboard album chart was ruled by so-called "classic rock" bands- Asia, Journey, The Police, Foreigner, Styx, REO Speedwagon, AC/DC, etc. I can't really think of anything that qualifies as "teenybopper" from that era... except maybe "Jesse's Girl?"

If anything, I think it was a bit of a golden era in terms of popular music. Rock and roll was the be all and end all. Stevie had three massive hits from BD, and I believe "Stop Draggin' My Heart Around" continues to hold the Billboard chart record for most weeks at #3.
I think Stevie's success was largely an artifact or releasing the right album at the right time. She worked with the hottest producer and collaborators of the time and was already a major name in her own right. She was still also young enough to be relevant to kids, yet legendary enough to appeal to their parents. She had all of the advantages of being a hot new rising star as well as the advantages of being a veteran household name. The planets usually align like this only once for anybody. Twice if you're really, really lucky. She had her moment; two moments if you count the
Rumours phenomenon.
Nobody has really been able to sustain mega-album sales throughout an entire career. Each of Michael Jackson's albums sold about half as much as its predecessor. Same with Janet Jackson. Same with Prince. And I'll bet Adele's next album (titled 25? 26?) will sell about half of
21. As for concert tickets, I suspect the decline in sales is largely due to the fact that she has pretty much toured every summer for the past 15 years (with a few exceptions) without releasing much in the way of new music. Audiences are a dynamic group- constantly dying off and renewing itself. By not releasing new music or repurposing her music for music/film/television, Stevie pretty much shut off her ability to recruit new fans. So as the old fans die off or become bored with the same setlist year after year, there are no fresh new a$$es to fill those seats. Indeed, by her last greatest hits (not a tour) tour in 2010, she was playing 2000-3000-seat venues at casinos. For IYD, she was back to playing 4000 - 10,000 seat venues.