Actually, what is the problem of sandbox if there is a perfect quest log ???
A lot of people don't like the grindy elements of sandbox. Repetitive stuff that you need to do to unlock something. For many, myself included, feels like working in a game. Obviously, some are fun, but I found most of them eventually boring and unnecessary. If there is no grind, it is simply easier to give the agent choices to pick where he wants to go.
But at the same time, there is a problem that most interesting and complex stories, like this one, need an order. That is the main reason why sandbox end up being a bad signal, not by construction but by correlation. Most complex, interesting stories need to follow an order, so the sandbox is just annoying. It works in games in which each route is simply a collection of simple routes with little interaction, but most of the time that implies that story is less involved.
So far this game has focused on story, so it is understandable that even with a perfect quest long, people will dislike the sandbox, either by the potential implications on the story (which I doubt is the case here) or the grindy elements.