I absolutely hate the system. Does not break the game for me. But forcing me to make a rival out of countries I have absolutely no problem with beecause otherwise I get maluses, it's terrible game design.
Im all for a rivalry system but it needs to be dynamic and realistic. Why do I need to rival as France egypt to fill up a slot? Why do I need to rival in early game England as Castille when in fact I want to ally them against France?
It makes no sense. Let me rival whoever I want, like, my actual rivals.
I understand for the IA you might have to force her to pick always 3 rivals at random, and thats fine. But PLEASE dont force the player.
The Victoria system is much better. Im not force to declare rivals if I dont want to. And i dont get penalised for not doing it, and its not an static number.
As mentioned by other it also creates a bunch of stupid problems that should not exist, like friends or neutral nations becoming rivals because they need to fill up a slot, no other reason, or smaller nations rivaling each other, while the real big blob rival looms next to them, waiting to eat them one by one while they rival each other.