If I remember correctly, the game of the year edition is extremely old. That is just the same thing as the original Sins. You do not have any of the content of the three expansions, Entrenchment, Diplomacy and Rebellion. If you hurry you might still make the sale on steam where Rebellion is 66% off, that will get you all the content you are missing.
Take a look at all the mods available for Trinity. Some may never make it into Rebellion. So that's a thing. I can't imagine my life without Sacrifice of Angels 2. Good gaming to you sir.
There is already a version of SoA2 for Rebellion isn't there?