A lot of the changes you could make in IV were not the kind of changes a Civilization/Country makes without being overthrown by a different Civilization/Country or having some kind of Military Coup from within (which I would argue does change the civilization to a different one). There were a few changes you could make that made sense, but overall many of them were so drastic that it didn't really make sense. For example, you could change from Freedom to Communism in the span of a turn and still be the same society. In reality the only real way that would really happen, without it taking several hundred years of slight policy change from one to the other, would be an overthrown government. And in that case, it would not be the same Civilization anymore.
That's why there's anarchy. And the more changes you make to the civics, the longer the anarchy lasts. I find it very easy to roleplay in my mind that that's what's happening to my civilization. About the timeframe of anarchy: sometimes a turn can be decades, sometimes a turn can be 6 months. So yea, it does kind of break immersion as the game progresses, but it's a fine balance between realism and gameplay (you wouldn't want to be punished by having anarchy last longer towards the endgame just for the sake of realism, right?). I loved the civics system because of this.
I find social policies very unrealistic and it kills my roleplaying experience, despite it being an "RPG device". Why? Because in RPGs where you build up a character (a person) then assume its role, in civ, social policies are used to role play my civilization which is a collection of people. A SOCIETY. And Societies change much more than individual people do. My hero may not unlearn his swordfighting skills in an RPG, but governments and societies change all the time. Having my civ realize it is "honourable", then forcing it to stay like this for thousands of years is neither realistic nor is it fun.I tend to like this way better because a Civilization does grow and build upon itself. A Civilization rarely goes through drastic changes without becoming a different Civilization. I think the way Social Policies are now, it mimics the growth of a Civilization better. This particular game mechanic tends to make you think about what you want your Civilization to be and how you want to play before you get very far into the game. I think it works better because you have to balance all your goals. You can't just change between warmongering policies and peaceful cultural policies in one turn. Granted, the policies could be better though.
Japan is a civilization that used to treat honour as one of its most important societal values, but after the defeat in WW2 their constitution no longer allows them to militarily interfere in international conflicts that do not involve themselves. I can't do this in-game because once a society decides it's "honourable", you have to be an eternal war-monger to reap the benefits.
What about the USSR, the Third Reich, China and its many civil wars and turmoils? What about Rome and France's revolutions? No society in history picks a policy and stays the same way for eternity.
That's why I HATE social policies. I'm not playing a hero and building a character, I'm playing as a civilization, and not allowing my civilization to change according to world politics (in a game called Civilization, no less!) is just absurd.