I don't know how other people feel about this, but I always felt like the strategic resources weren't useful enough in previous civ games. It may be because I was always playing on Marathon game speed, but I always felt like I had more strategic resources than I ever needed. Occassionally I might run out of oil for planes, but I never felt the need to wage war over these resources. Iron was one thing that I almost never needed. Thinking of Beyond Earth, air units don't even require any strategic resources at all.. I wish that there were more units in Civilization 6 that required strategic resources this time around which would make them more valuable and worth warring over.