This game is easily one of the best assassin creed games ever made , the exploration is probably the best out there is and it doesn't make you force to do these side things if you don't want to and just play the main story so yeah that option is there for you. I read one review where the guy gave 6/10 and said that narrative wasn't compelling because of points like:-
Why are we going to England ?
Simple for making alliances and finding a new home so that we could protect our clan's pride from King Herald of Norway.
Why are we making alliances ?
Simple , so that they could help us all united in time when Raven clan would need their help.
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 !