Crisis Civil War is one of many things that Civ gamers would have to get used to with the Civ VII system.
Civ has ALWAYS been about the Steady Upward Progress to Victory. Anything that impeded or even modified that in any negative way was to be avoided at all costs, including save-and-retry or rage quit.
But Civ VII has been designed specifically to change that.
You WILL be seriously impeded at every Crisis Period. That's what they are for. You WILL have to start 'fresh' (well, relatively fresh) with every new Age, whether you want to or not (at least until the Modders give us Forever Civs in Civ VII, which should be within the first week or days after release).
Those that cannot get used to it will either play only modded versions of the game or not play at all.
So, all the discussion about what players will accept is slightly off the point: the game is Designed to force them to accept a basic difference in how the game plays, and that will, inevitably, be utterly unacceptable to some no matter what other 'tweaks' - like Civil Wars - you add to the new system.
Meanwhile, those of us who have already decided to give the Age-and-Crisis type of Civ game a shot are not likely to be excessively put off by the fact that there is a new Civ in town from a break-away set of Cities/Settlements when the new Age starts.
Especially if that (potentially) happens to every Civ in the game, both Hummie and AI-run. In fact, that is likely to be more of an impediment to the AI opponents than to the human player, because the human player tends to be much more adept at finding loopholes or ways to 'game' such systems: as I have posted before, I frequently see AI Civs lose cities to 'Loyalty Flip' in Civ VI, but I quickly learned how to avoid it and it is simply not a problem for me - or, I suspect, any other human player. Expect a similar result from any Civil War system in Civil War VII: it may hit everyone, but the human player will react to it better than the AI and probably learn how to frequently turn it into an Advantage rather than a Set Back at the start of each new Age.