Beach Map and there are others like it that are very linear. Where you go from the start and at the end is the area for the boss. Even the story is the same way. After playing it long enough you will know what general direction to go to get to where you want to go. That is because no game has endless layouts of the same area. That is true without any arrows pointing the way. No doubt D2 had the same problem.
What I am saying is the truth, no game will have endless numbers of layouts of the same area. That would be impossible for any game to do and D2 is no different.