There aren't, in fact. The game only has room for so many units, so many buildings, so many abstractions. There are always limits. Games designers tend to work better because of them. A lack of a limit leads to infinite scope, and reduced decisionmaking. It's the same in software. It's why we have specifications.There are, presumably, an infinite number of changes one could make in moving from one civ # to the next.
If the appetite for dramatic change doesn't widely exist, then that's just the way it is. It doesn't mean this lack of appetite is wrong. It's just not a demographic I'm a part of.
It can be, for sure. Everything is useful data.This can be seen as a positive as well. The developers now have a much better sense of the expectations, desires, and red lines of the wider Civ/4X fanbase. There is still a lot of potential design space in this formula; some of it is being explored by other developers now. Surfacing some of the soft limitations may help feed into future success.
But it's very muddled by the state of the game on launch. People were baffled by transitions eating units for months, due to the complete and utter lack of ingame signposting. Regardless of anyone liking the mechanic or not.