Sooo many things to reply to. I'm gonna miss some stuff, so forgive me if I screw up my responses.
First, I think the easiest and best solution to the problem of boring cultural victories with no choice is to change the conditions for a cultural victory.
The Piety-Enlightenment exclusion did have an excellent opportunity cost that Seek pointed out. And that is what I was saying about the strong synergy. Because they were exclusive, they had to do similar things to fill the gaps of the other, so if you were allowed to pick both it would be painfully strong together.
Enlightenment did not need to be nerfed. Neither did Piety. Some change had to be made that would weaken the synergy but not the trees as a whole. If this is too difficult to achieve (as evidenced by the fact that everybody is getting worked up over the changes) then perhaps we should just go back to what we had before.
@Txurce: Yes, we are both aware of why we are pushing in opposite directions here. But I certainly don't think that the Enlightenment tree should be only for Science wins, all VC types benefit from tech (though culture the least I would say). And I don't see a problem with changing the optimal strategy you are envisioning. The AI can't even handle basic synergies, let alone these massive slingshots you are planning to use the Enlightenment tree for. When I said its a finisher, thats the point, I meant that a finisher is not the point of the tree. You say that putting a GS at the end of the tree gives primary users a useless finisher, and I disagree. I also think that, since its a finisher, thats not a terrible loss. They already got the whole tree, isn't that enough?
I think the Enlightenment tree looks even better in Thal's current proposed model on this page.
Thal, please take my comments lightly. I am just trying to explore the possibilities. I haven't been playing VEM lately, I've gone back to vanilla. This is mostly because the AI still sucks, and everything feels overpowered in VEM. Which is a design goal, and I honestly agree with that goal. I just feel like its either too easy to roll the AI, or I move up one difficulty level and get rolled. So instead I've been playing hotseat against myself, and am noticing many differences from VEM, some that I like and some that I hate. So I have much less experience with the changes you make, and am basically only talking about theoretical stuff. So if you want, feel free to ignore me.
I'm sure I will come back to VEM at some point, and I still check these forums multiple times a day to see what's going on.