Here's a suggestion for you.
Instead of playing the same old war-rinse-repeat (which we all know works wonders because no game in history has had an efficient strategy war AI), why not try for one of the other victories?
Instead of expecting Firaxis to tell you sheep how to have fun, why not make your own fun in the game?
The problem is every other aspect of the game is as easy as warmongering. Everything not warmongering is production oriented, even culture. There are just a few more ways to skin the cat outside of warmongering, but it is the same thing, instead of mass producing military you are mass producing culture or industry for the various ways to win.
Militarily speaking, Civ5 has failed, I agree with you that there is no smart war strategy game AIs. Up to Civ4 it really didn't matter because the AI had a significant advantages and there really wasn't a lot of tactics required, AI was challenging because of the sheer volume it was able to throw at you.
The AI can't do that in Civ5. There are significant bottlenecks for military now without stacking, terrain is more critical and bombardment is far more effective than it was before and the AI can't make logical tactical decisions and never learns from what players are doing.
AI is not capable of basic strategic logic of putting melee up front, ranged behind, protect bombardment units, build and hold rather than create the lemming congo line of failure and then hit with force.
The difference between a passable AI and a terrible AI is how intelligent the AI is. They can't think and can only execute what they have been instructed to do so they are limited by the scope of the programmers.
While Civ has more parameters and is more complex than say a game of Chess, a computer Chess AI is passable because the coders have got to the point they can react to what a player is doing. Civ5's AI is horrible. It is horrible at a military strategic level and it is horrible at almost every level.
I was messing around with a game I was experimenting with a few things and wasn't taking it seriously when I was attacked by the Russians, she had 10 cities and I had 2. I was able to bottleneck the AI on land and had a big advantage by sea, one thing I have noticed the AI is extremely poor at building naval or air units. She tried to offer peace but I kept rejecting. If I moved out of my defensive position I would have been crushed, but she couldn't break through the bottleneck. It was a stalemate, but i was backed into a corner and she was rapidly out-teching me.
So she offered peace again, this time offering 5 of her 10 cities, including one very close to her capital. I took it. One shocking AI decision put me from a bad situation to a ridiculously good one. I loaded up the with military, piled as much as I could into the city adjacent to Moscow and attacked again not long after and wiped out the Russian player.
That game was effectively over at that point, playing it out would have just been going through the motions.
If the AI is too simple it doesn't make for enjoyable games. I wasn't even playing that game from a military perspective, I just built enough units to defend my two cities. The AI capitulated without having lost a city or had one in any real danger.
You just can't put out military units and mechanics like they have with Civ5 and give it an extremely basic AI, it totally kills the non Player vs Player element and the MP functionality is currently woeful and unstable.
Other than graphics, or other stuff I have no experience with, ie modding, Civ 5 is significantly inferior than Civ 4 as a game, in every way. This feels more like a console game than a Civ game.