You are not comparing offense to offense, you compare offense to defense, for example
Defense Cannons (anti-cavalary guns) get a 10% increase in damage in each age, while in IA it gets a 50% damage increase to cope with the huge increase of cavalry hp ( when they become tanks ) so that's like 5 ages difference
Also air units (which are extra increase over the basic +15 troop space increase per age) are devastating vs EA defenses and are much more important than the +15 troop space
Furthermore, IA is the most increase in number of defensive buildings among all ages (1 mortar 1 ballista 1 tower 2 air defense 2 bunkers 2 caltrops 2 spikes 1 ambush 2 alliance gate upgrades)
So there is no way on earth to compare it with other ages gap