This is an adult movie with an adult message.
I'm not going to talk about the silliness of the movie, none of that exaggerated stuff really happens in real life.
Most of us go about life forgetting the things that truly make us happy. Somewhere along the way the circumstances weren't 'right' to continue creating. Or, for instance, it had gotten too difficult to continue creating and to drop it, whatever it is that made us happy, was the 'right' thing to do.
So as life goes on we continue making the 'right' decisions that are accepted by the society and forget that we look like puppets going about life with our eyes closed.
The main message in Dirty Grandpa is to wake up. And stop 'sleepwalking through life'.
The movie is incredibly silly, it's sometimes funny and in my opinion has a very strong message.