The usefulness of the other buildings are much more situational. While some of the boosts to victory points can be useful that is only true some of the time. Camps give an immediate return and if you are working with other guilds (or at least not going all out and letting chance decide if camps will be kept) traps would not be taken well. Also traps are only good if there aren't enough camps to offset them after all they double the attrition you'd get IF you get attrition.
I've seen a few fortresses utilized to delay some advances but generally better to simply kill faster than your opponents and use softlocks (i.e. sectors mostly completed so you can flip them when you want if someone else attacks them) on sectors effectively.