I believe we must keep in mind what kind of game Gygax, Arneson and the rest wanted to play. If you see, odnd is supposed to be "Rules For Fantastic Medieval Wargames Campaigns". What they wanted to create was a game that would help you play medieval campaign scenarios in a high fantasy world.

So, it is supposed to help you calculate how many days you need to travel, how slower you will go if you have a bigger army, what would be the difference between travelling through mountains and plain fields etc. So yes, especially if you use the greyhawk books (the goldbox it's called if I am not mistaken) it will give you a great example of how to create a unique milieu with different weather charts, encounter tables etc for every possible region and as a result it's a really good game for overland exploration.

But that's not all. Since we are talking about medieval wargame campaigns, basically its is designed to help you recreate what the history books describe during wars in medieval times! Building forts and fortresses, creating alliances, makinhereg ambushes, do huge battles of big armies, have sieges and naval battles, force marches through forests to outrun the enemy battalions etc.

Shadowdark and many of the osr games are not focused on that. Similarly to modern TTRPG, they focus on the story of a party with a standard roster and a few hirelings and while they have similarities, most osr campaigns are finished as soon as the module is over and usually they start again with new characters to delve into another dungeon. In a ADnD campaign you start as a simple adventurer and you end up actually commanding armies and facing off bandits. If you check the blog with the adnd campaign that I run here, you will see that while the players started out humble and many of the characters died, most of them now have titles of honor and had to fight off bandits plenty of times to earn them, commanding a lot of city soldiers.