PR person here - I know, I'll duck the rotten tomatoes.
I empathize. I have a similar rant about mommy bloggers and one client or another at least once a month. Still, I'm not in the celebrity business (thank god) so it's rare for me to field that kind of attention.
I take some issue with a few of your points, but I agree the system is broken. These publicists sound terrible.
-There are PR people (like, ahem, me) who have never pitched The Stranger because we know we have nothing newsworthy for this audience. You just never get to meet us because we're so darn polite and busy pitching some paper much more suited for our clients.
-Anna Kendrick was probably contractually obligated to publicize the movie way before her part was even filmed/edited.
-Scheduling 30249534523409098 interviews in one day when you have a hotel room reserved for four hours (and 15 minutes of set-up) is not ideal for ANY publicity team.
-Particularly since, as you pointed out, reporters typically ask the same questions to death.
-The bass was undoubtedly there for the one random reporter from Topeka yelling "I need B-roll of something!!"
Related: The other thing is that if the celebrities go off script - I know this is a shocker - many of 'em are kind of doofuses:
Sadly, it's just safer to give them a script (and many people feel more comfortable with one - they're actors, after all).
tl;dr Our job is to help you get the best story you can. Sucks that didn't work with these guys - please don't paint all of us with the same brush.