No they're right. There were too many units in the modern age. It was great for the WWII Scenerio, but in the actual game they saw little use. There were Alpine troops in Civ II as well. 5/5 treats all tiles like roads.
However, you didn't have as many units in the non-modern ages as we now have in Civ IV. Axemen, Crossbows, Horse Archers, they really do add a lot more to the game than Paratroopers or Cruise missles ever did.