I'm having the same problem myself, although I personally take it as another incentive to attack and destroy all other factions
Seriously though, what version are you playing in? It would appear that diplomacy has been tweaked to be much, much harder in later patches (1.3-1.5) with the AI showing little to no interest in deals of any kind. Although I have yet to play a campaign for long in these patches so I'm not sure how the diplomats stats and your own military power affects the outcome of negotiations in the long run...
If you do like to solve things peacefully I recommend version 1.0, from what I remember all armies were possible to bribe (except faction leaders and heirs) and the other factions paid handsomely for everything from map information to alliances. Long campaigns with those possibilities do in fact get rather boring though!
Kind regards
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