And that's the reason why people like you won't work on projects like that, because you will always assume that it can't be done. ;)
Actually sandbox means every open world game or a game where you can have some choices made by your own. I know that sucks. I would really like that openworld games would somehow be divided from the true sandbox games like minecraft, dwarf fortress and garrys mod.
You are mistaken. There is no universally accepted (or even acceptable) definition. A "sandbox" can be "open world", but it doesn't have to be. Those are two different genres/tags/descriptors, but you can have one without the other. We often see "Open World + Sandbox", because they make a good match. The opposite of "Sandbox" is "Theme Park", a tag that can also be given to both, "Open World" games and games with a rather confined world building or even no noteworthy game world at all.