Infantry don't need a buff. If you know your military history you should know that, as technology has improved, foot soldiers take on a less attacking role - the soldier takes on a more supportive, overwatch or "clean up" role. These days tanks, artillery, smart weapons, etc do the major damage & infantry supports and protects these weapons. Tanks & artillery can take ground but infantry is needed after the fact to hold and defend that ground.
In this respect Dominations has gotten it exactly right. In the early ages footsies act like footsies should. They are strong and in numbers can topple huts and tents and town halls with ease. That's how it should be when considering armies fighting in the middle ages, iron ages, etc. As you get to Enlightenment and Industrial the weapons are improved and the footsies are better suited to sniping rss, TCs or cleaning up those last few buildings. See the similarity?
Instead of complaining about foot soldiers needing a buff, tailor your army to suit the age you're in - and adapt to the next age, and the next. If you're too inflexible in your thinking try another game - I'm told Candy Crush is popular.
One small problem...... The Heavy Infantry and the Ranged Infantry carry the same weapons as of Enlightenment Age on. With that in mind, they would have a similar range. If you want to insert history in this, every foot soldier in your virtual army is a musketman. This would go best with what I am about to suggest. As of Enlightenment Age, the Heavy Infantry and Ranged Infantry would assimilate into one single unit.
What would this mean for nations, one may ask? It would mean that it will boil down to either an Infantry or Cavalry/Tank unique. This will radically change the uniques for Infantry, either way. Of course, we would need to balance the stats to make it sound for EA on.
Now back to my attack on this post. Sure they would have some cleanup role (not like that changed since the dawn of time), but I'm pretty sure this would also mean that your city builders would advise placing TC inside. Also, unless I had a shotgun or some other weapon designed to be used close range, why on earth would I intend to shoot my weapon at a close range? I would not. I would try and shoot it as far away as possible without having accuracy a detriment. Speaking of which, I must be training an army of supersoldiers as they have dead-eye accuracy.
Since the cannons have made castles obsolete (as told in the in-game description), I have not seen any change in the structure of the castles nor the walls to reflect angled fortresses that aim to deflect the shells up and not try and resist their force. I might have noticed a slight change in the geometric look in the walls from Lvl 9 on, but it still has that vertical look. Plus, the invention dynamite and other concentrated explosives have made walls obsolete. Actually in any siege ever done, all you would need to do is bust down one segment of wall, and all your troops would go in and kill all the men and..... You get the jist. Oh dear, I almost forgot that gates exist, so wouldn't my army just utilize the gates they can easily bust open and get into parts of segmented military bases? I mean, if history became a huger factor in this game than it already is, then this would happen I'm quite sure. But then again the troops have the brains of Goombas.
About the tanks..... They have equal capabilities of artillery of busting down gates and walls albeit at a closer range. They can just ram the gate if you ask me. So tell me this: Why would I keep walls if they became obsolete? It would be painful to get the funds to repair those walls everytime they get shot down. So as you may read this, you may figure out that history would trump any balance the game has. In fact, tanks are quite good at ramming. They would smash into the buildings just by ramming into them. And don't get me started on ammunition. This game has troops with infinite ammunition, certainly not historically accurate.
So here's the thing: Do not attempt to use actual history to debate balance in a strategy game. It will only end up being used against you.