Nick represents the innocent person who just wants to be happy.
Amy represents the people that do evil. She does things that she could do differently to live a better life. But she does those things anyway and makes Nick and all her exes suffer.
What people think of Nick and Amy is the simple view of everything. Taking the simplest truth and making huge judgements based on something that might not be true. Not looking at the entire picture.
The story goes back and forth between different views and we have conflict. People act on their views of what is happening. This is a pretty good movie. I enjoyed it. Lot of people might not. But this kind of thing just takes you to a different world for 2 hours and that's what I want I guess.