But as a game mechanic it functioned as a means of building local alliances against the "others". It also provided alternative means of upping happiness to boot, something the AI COULD grasp. And you're basically in the camp that believes AI should play like a human to beat a human, not that the AI should provide resistance for the human to overcome. Religion was fine for me.
No where in my statement did I say AI should play like a human.
AI's need to treat human players as 1 of many which is really the cornerstone of Civ since Civ3 and there's nothing in my experience with Civ V that would indicate otherwise. Humans will ALWAYS have advantages over the AI.
When I put on my rose colored glasses and talk about Civ3's sandlot I was talking less about human interactions with the AI, but how AI plays against its environment, humans included.
Sandlots by default mean equality, AI's will attack when you are strong, and be more passive when they are weak. The great thing about Civ3 is that it has these high level treaties that collectively work like the great power alliances of Europe. The MPP domino effect was a common sight. And underneath these high level alliances are a series of flexible treaties. ROP (open borders), lump sum tech/gold for perturn gold trades. And despite no formal guidance and no hard coded 'pacts' the AI can through geography, mutual alliances and some chance form power blocks X,Y,Z in a loose coaltion against A,B,C. That is FUN to watch and creates interesting dynamics and politics.
So what you ended up with is the low level AI working to evaluate its position, lots of intrigue. Alliances made and because there's no 'vassal' system, the game remains dynamic.
My biggest gripe with vassal states is it narrows down interactions in a standard map game very quickly from the 8 civs you start out with down to 3,4 sometimes only 2 civs, because everyone else has been eliminated or has become vassals or someone else. That's not to say this doesn't happen with Civ3, runaway AIs will eat everything in its path, but it doesn't always happen, whereas Civ4, Vassal State hanger's on is reliable in every game.
It also removes what I call 'power arbitrage' from the game. When all the weak Civs are aligned by hard coded pacts to this or that other more powerful Civ, as a human player you can't influence politics as much, because you tend to have to deal with ther masters.
In Civ3 you could sort of buddy up with a smaller Civ on the edge of a large AI you're targeting and use them as your proxies.
That's in part because Civ4 chose to go with very restrictive hard coded diplomacy, rather than the looser diplomacy of Civ3.
It's 2 different approaches with a similar AI. Soren programmed both. I much prefer his first attempt, which while opening some exploits, created a dynamic diplomatic environment.