I obvisouly haven't played the game. I watched the first chapter video and what I got were: bros need to fix the car and Cindy told them to collect shit first, bros need to rent a boat and dude with the boat told them to collect shit first. It seems fun to run around the map fighting mobs and collecting stuff, but that's not story. And yeah I have no doubt something is missing in the beginning. They put the opening into a movie.
don't worry, its not really a problem.A lot of the things introduced in the movie will surely be explained in the game, even if in passing conversation