All it seems you're doing here is repeating that you revel in imbalance. That civ on flat plains is not operating on a remotely even basis. The fact that it has to focus on survival is not an advantage over the civ that gets to turtle in the mountains. In threads like this and the raging barbarians thread, you want to push that imbalance is fine and should be maintained because you enjoy getting lemons as much as cherries.
It's interesting tactically if there's give-and-take, if the plains civ gets some strength that can be leveraged in lieu of the mountain bonuses. As it is, what you seem to be advocating is a kind of masochistic thrill dealt by lopsided bonus distribution.
Some of this is subjective, obviously. But I don’t think the game needs to be completely balanced, i.e. it’s okay for some starts to be stronger than others. But it’s also a matter of degree. I think the power of Mountains over Flat Land is basically okay - but is a little wonky less because of Mountains and or Campus adjacencies and more because of other mechanics.
I think this is where it’s got a little messy, because my comments on this thread have got a little muddled. My original post was really about pointing out what a huge impact Mountains have on how your game plays. It was really just an observation rather than a complaint or call to action.
We’ve then got into a discussions about population being undervalued, Science being too easy to get, and what’s wrong with Rationalism. Which unintentionally circles back to Mountains, because Mountains = Campus Adjacency.
Perhaps this post even further muddles that, but hopefully not.
So, basically my view point is this. I think: Mountain starts are strong, but that’s mostly okay; Science adjacencies are in a good place in terms of the “puzzle” of where best to place Camouses, with their mixture of +1 and +0.5 bonuses and slight clash with Holy Sites that also want Mountains; however, Science in general needs to be harder to get overall (reduce Science from City States, soft cap number of Campuses and or push back Campuses), Rationalism needs a complete re-work, and Population / Farms / Flatland needs some sort of buff (but ideally not a buff that just creates more city spam or high pop in every city).
If you want more concrete suggestions on Science you can look
here. If you want my views on making Population or Farms more valuable, you can look
here and sort of
here (on that last link, one thought I had was that if we had additional governors that unlock mid or late game, some of them could be focused on buffing Pop a bit like Reyna and Pingala do).