So... Are you suggesting that the developers just make up a new civilization that never existed as a successor to the Mississippians? And similar for others that don't have obvious historical predecessors and successors?I think it is a matter of creativity. Imagine Mississippians with a crisis event of Great Flooding (something that happened in America long, long time ago in very ancient times) that forced them to became more maritime civ... Still civ-switching but provided some plausability.
I don't like the idea of made up civilizations.
But to me, that's less immersive than what we have now. Making up new civilizations is just weird. Also, in the real world, there are sometimes rather large cultural changes in an area. The example that the developers used of Britain is a good one. It seems that most people are OK with "Rome -> Normans -> Great Britain", even though the cultural differences between Roman Britain and Norman Britain and Great Britain are massive. So, I don't know if "cultural link" is the right phrase here. I think people just want historical accuracy, which is frankly impossible for most civilizations.To keep the immersion, the flavour, the cultural link between all civilizations so that civ-switching is less painful. As in the previous Civs.
It seems limiting, though. You suggested that only certain leaders could take particular paths, for example. No more Charlemagne leading the Mississippians, for example. That's definitely more limiting than what we have now. Letting us mix and match leaders and civilizations provides some benefits. We can have leaders that we wouldn't otherwise have and we can try different strategies that would otherwise be blocked.In my opinion it would not limit much but this is my viewI think they just lack of creativity in that matter (see my answer at the top). That said, my perspective leans heavily toward single-player gameplay, and it may not translate easily into a multiplayer-focused environment—so you might have a point there. In multiplayer oriented-game there is more focus on generic solutions, applicaple to all paths/civs/leaders in similar fashion whereas my ideal solution would require more flavour, event-driven approach.