This is the real interesting problem. Even simple subtle decisions like "should this list be kept sorted, or have new things added to the end" determine under what conditions you will hit a new conflict and when you won't. List of enums, add to the end, and if 2 branches grab the next enum value then you'll see a conflict. List of lets say URL prefixes keep in order, then most randomly added URL prefixes will not collide or conflict, only conflicting if you get 2 things trying to operate on the same prefix.
That doesn't mean that Git couldn't have a much better UI for this problem than it does. And while I agree that Git seems to have mostly won over SVN and Hg, it doesn't follow that it's because of its UI. (For example, I think that a lot of Git's success actually comes from the UI of GitHub, not Git itself, but I don't have evidence to back it up.)
Take a look at the Research section at the bottom of https://gitless.com/ for work that's been done on how to accomplish the same operations with a simpler conceptual model.