I find the side missions repetitive as well. It's always "go till the end and defeat the monster".
BTW, you can finish side missions much faster and easier by avoiding the battles. Just "hug" the walls while walking around the map, this will avoid most encounters. That way you can walk straight up to the "boss".
“The only way to deal with an unfree world is to become so absolutely free that your very existence is an act of rebellion.”
- Albert Camus