I think there are no scripted events in the game right now. Its just a new players thing. People do not know about secret agendas, do not use it and do not know how to. I play Catherine emperor difficulty several games and they do not declare on me. Reason is you know thy secret agenda from the get go and can play around it. Actually you need to play around your closest neighbour, maybe 2 closest neighbours. Others cant declare a do a thing at all. And the best way to uncover agendas for other leaders is to gift them 25g on the first meeting. Thats +1 level of access. Then you can send a caravan to their city. Thats +1 level of access, uncovers secret agenda. Then you play around it and get just a mediocre units to fight barbarians. Usually you wont need more forces until industrial if you properly play around agendas. And using secret agendas is a whole new dimensions most people havent uncover yet. Its fun!