I agree with almost everything on the OP, but this thing make me really angry:
* social policies should be more flexible, an empire should be able to change it's directions over the ages
One must be extremely narrow minded to say that.
1st - They are flexible. You are able to change the direction of you civilization over the ages. Don't you know that? Let me give you a tutorial then: when you accumulate enough culture, you can chose a NEW social policy, thus giving your empire a NEW direction, if you like. Otherwise you can reinforce the direction it is going right now taking a social policy from the same tree. Don't you know that?
2nd - people often mention the Civ IV system as a more "flexible" system cos you can adjust to the situation and blablablablabla.
Let me ask you something: when the USA declared "war on terrorism" and invaded Afghanistan and Iraq, did they change their "Government Civic" to "Police State" to prevent unhappiness? Believe, if they could, they would. Ask Bush.
Since China has a lot of people and need infrastructure, should they change their "Labor Civic" to "Slavery" and whip some, and then return to whatever they are, right? Yeah, go try that.
Remember what happened on the US when they wanted to end slavery on the whole country? I tell you what happened: a freaking civil war, a bloodbath that still carries grudges today, 145 years after (I know that's more to it than this, but let's keep it simple, my example still applies). So you think that over a million deaths, A MILLION, caused by an internal war that had amongst her reasons a "civic change" are well emulated by a ridiculous turn of "anarchy" where you just lose a turn of production, gold and science?
Ever heard of an obscure little thing called the "french revolution"? It was a civic change! Should I go on?
There is no "flexibility" in real life, you need a freaking revolution or a "coup d'etat" to change these things in real life. So why you make a game where you can just go back and forth on this, whenever it pleases you with no major consequence?
Hell yeah they should cut this flexibility! This NEVER existed! A gradual upgrade of the thought system indeed ocurred as time passed by, but using those civics from CIV IV, it could only be well emulated if you had no control on the changes, and with the changes being progressives 90% of the time. No government wakes up in the morning sayin "hey, we were a war mongering people our whole history. Let's change that and produce more culture!".
The entire middle-eastern are warring for THOUSANDS of years! That land knows no peace, exactly cos of the type of society that they cultivated since the beggining of their history. Time passed, things evolved and were adapted, but following the same mentality. Go ahead and call them, say they just need to change civics and everything will be as colourful as the rainbow. Good luck with that.
The English carries a "fame" all around the world for being punctual, methodic, arrogant for centuries. The French carries their fame, the Scotts carries their fame, the Portuguese, the Turks, the Russians, and dozens of other cultures and countries, they all carry their fame for centuries based on something cultural that are carried over through the generations. Adapted to the new times, yes, but it's the same thing in essence.
So don't come with this "flexibility" bs. This thing doesn't exist and don't need to. That's the early choices that has to define what you will or can be in the future. You compromise and learn to adapt yourself to every situation by being what your people always were. This overpower gamer mentality to take advantage of every possibility every time it's the best choice is ridiculous. Learn to play with the inconvenient or non-optimum choice. That's what strategy is, you adapt what you have to the situation. A football coach doesn't sign an entire team every time he'll play with an adversary that has players that overcome his own. He adapt his strategy to deal with it.
That's what a lot of whiners have to do.