I cannot seem to figure out how actually engage in any trades with the AI. No matter what I ask for (nothing) or what I give (everything), the deal is somehow unacceptable. The AI seems to refuse to consider even trades as blatantly lopsided in its favor like "Here is $1000 for free". Is this feature simply broken?

username wrote:Is this feature simply broken?

Just not implemented.

Haven't even noticed this feature is supposed to exist

Don't honestly think it is a good feature. It lends itself for abusive behaviour towards the AI. It requires a lot of AI scripting to prevent abuse of the mechanic and even then, it will become quite apparent that the AI is not actually playing the game.

e.g.: Siphoning tech from friendly empires or gaining advantage before an invasion
Galciv has put so much effort into this part , they had huge experience wit past games and still the AI lets itself being played like a violin.

Would much rather see the AI take a base competitive stance towards all others and play its own game
Would also spare the player the not so fun mechanic of "farming" the diplomacy screen in regular intervals

I don't really think tech siphoning would be a problem, since you can't trade techs on the trade screen anyway. The only tradeables are currently money, metal, and planets. But the AI won't accept or even consider any offer, including those where I simply offer to give him free stuff.