Great discussion here, I love the general direction where this is going!
I haven't played for months and currrently play a mostly unmodded game to get a feeling for vanilla again (I started using Thal's mods only weeks after the 1.0 release and rarely came back to the unmodded game).
In comparison, the unmodded game seems sluggish. It takes ages for any new city to develop. For dozens of turns, any new city is mostly concerned about itself, building up basic infrastructure like monuments or granaries. If I want to have a specialized city for e.g. unit production, I have to wait for 2 eras until it has the needed infrastructure like a barracks and some production-boosters.
It feels like there are so many buildings I won't ever build (at least not in the era they thematically belong), so there's the feeling I'm missing a lot of content here.
IMHO, CEP's easier rush-buying helped immensely to get other cities than the capital up and running in reasonable time, which was fun.
Don't get me wrong, I fully understand that too much production results in all cities getting every building and specialization is pointless again. But that wasn't the case in CEP. It rather found a solid middle-ground, whille the unmodded game feels production-starved.
In other words, the amount/density of choices the player has to make were much higher in CEP. You didn't hit the "next turn" button as often without making any meaningful choices during the turn. "Choices are fun" always was one of Thal's main philosophies.
The lower gold purchase modifier allowed to react quickly to several situations. Whether you want to settle an newly found fertile island quickly, start a quick offensive after you spotted a weak spot in your rivals defenses, or wanted to quickly react against hostile actions from other civs, you could do so.
Mind that this didn't mean you could do everything at once! It only meant that IF you had stockpiled some money, you had some power to react quickly to new situations. Once you spent it, it was gone. But if you had a full treasury, it meant awesome choices, which were nevertheless hard to make.
Another field where I feel the unmodded game offers to few choices is tile improvements. We rarely have a meaningful choice what to build, there's always an optimal solution. CEP wasn't as much "autoplay", mainly due to multiple improvements being boosted by freshwater instead of only farms.
Speaking of this, why do you find a gold boost from freshwater for villages weird? What about riverside trade?