It seems to be kind of a strange complaint, that the objectives either lack variety or are repetitive. Not sure as I haven't done much in campaign, but so far through challenges, you can:
- repair
- escort
- demolish
- heal
- hack
- capture
- and deliver
various objectives. These will be used in tandem with each other to create a mutli-part mission that is, if only through the order they are done, different from the other missions.
If you're talking about the IGN review, it also seemed like he was annoyed that objectives were dependent on map. Also, that the story is repetitive? Can't you skip the cutscenes?
Just seemed a bit off.