Actually I think this is still possible in newer games, I always find myself pivoting to random win conditions I wasn't aiming for, in both Civ5 and Civ6.
Although, perhaps you are right about it. I get this idea where if I want a science victory for example in Civ6, I need to plan ahead where all the campuses are going to go for max adjacency and such.
I think 6 has plenty of flexibility. The only times I sometimes need to plan that far ahead is if my capital/production city only has like one flat tile, I might loosely pin that tile to avoid accidentally killing my on spaceport site. Sure, obviously if I aim for a culture victory I tend to want to get theatres out earlier than otherwise, and I'd probably chop a little less and start to think about where I might eventually want national parks. But there's multiple ways into the culture victory that often I will have just been playing normally and then when I get to the mid-game just accidentally realize that culture might be an easier win than space, even if I have a science-focused civ, just due to whatever random reasons of my land and area.
But definitely I would hate to have things so restrictive that if I don't have a theatre built in the first 50 turns I don't realistically have a chance at a culture victory, or if I don't start optimizing my diplo favor then I don't have a chance at diplomatic victory, etc...