Here's my take:
I don't mean to offend anyone but I think the young kids (ie children) don't care about the actual wrestling. All they care about is seeing their favorite stars in person and seeing that star win (like John Cena). Many of the children are too young to appreciate the technical aspect of a match or the actual excitement level.
Some of the parents who bring these kids to the shows, don't know anything about wrestling, they are just taking their kid because the kid wants to go.
There are always the knowledgeable fans, hardcore fans, or technical wrestling fans, who actually like everything, seeing the stars, the match, the promos, etc but those fans are in the minority.
Also, there are too many distractions for the little kids.
Concession stands, souvenir shops, etc. This distracts their attention.
Finally, I think it has to do with accessibility to the stars.
"Back in the day" when there was little TV exposure and no internet, the only way people could see their favorite stars was to actually go to an event. Therefore, when the fans were there, young and old, they were really into it. Nowadays, kids can simply go on youtube and watch whatever wrestlers they want or buy the DVD of any matches they want so when they're at the show, yeah it's cool seeing the stars in person but the match is "boring."
In the Attitude Era, the fanbase was predominantly the older crowd (teens and above) and the fans were into it because the wrestlers kept them engaged in the show AND because of the shocking things that were happening.
Anyway, that's my two cents.