Yes, most of the code will never change. But some of it will, and it's sometimes hard to predict what that will be. So, to an extent, all of your code needs to be written so it's changeable in the future. It doesn't have to be enterprise java style to be flexible -- just well encapsulated, and testable code helps with that.

Also, it seems like people in this thread who haven't used angular see that word -- factory -- and think of endless crappy java abstractions. You are overestimating the overhead that angular is bringing into your application in this case. A factory is just a component that can be shared between controllers. It's a singleton, like a lot of sharable components in vanilla Javascript applications, just with a defined way of being injected into the controller, and a way of declaring dependencies.

If your problem is with object oriented programming in general well... I can't help you there.