you don't seriously think they added slow-mo to make the runtime longer?
i mean come on, if you did speed it all up almost all of the shots would be over in a second and lose their effectiveness.
there's nothing wrong with having a style, it's not like Mission impossible 2 where the slow-mo was gratuitous, here it was stylised and i honestly can't believe some people think they just added it to make the film longer, or are they just exaggerating to be funny?
either way, if anyone does seriously believe they only did it because they didn't have enough depth then that's kinda weird if you ask me, i don't think the film would be close to 2 hours if that was the case, yes i know if you did speed up all the slow-mo it comes to around an hour but, like i said, that would lead to the more dramatic shots being a second or so long and losing any kind of effectiveness.
slow-mo is not something you can just add later, or you can but post converted slow-mo would't look anything like the slow-mo that this movie was filmed in.