Why am i playing as a god in Asgard ?

For that you need to complete all the main missions , animus anomalies and the Asgard quests.

So that's why i think that you should first complete these entire things to judge the overall narrative completely instead of just playing it for 15-20 hours. Good thing is that the storytelling in the game is so interesting that completing the above things won't feel like a task , especially animus anomalies !