I think the offensive injuries and the not knowing exactly how the back ups would respond caused some of the conservative play calling.
Last year the conservative play calling was blamed on distrust of the QB.
This year it was first "playing it safe" to keep Manning off the field, and next "limitations" because of injuries.
I think Kubiak is just a conservative play caller. That isn't necessarily good or bad, just what it is. Personally, I would like to see more aggression at the ends of halves, etc.