When you read MMORPG-related blogs you will occasionally stumble across one that tells you that WoW is actually not just a great themepark, but quite a good sandbox, too. You just need to make it one! It is all in your head. The blogs usually argue that you can, for example, explore.
But exploring is not really something sandbox specific. After all, you can also explore a box without sand if it has any interesting, but fixed, structure inside. Can be fun, is fun for a while in WoW, but sandbox? No.
Alternatively, you can skill a profession while at any level. But training a profession doesn't really change the sand in the box. It just changes you. And nobody sane would deny that WoW gives the player ways to change his character. The entire endgame is about building a char with the help of loot. But sandbox? No.
What else can you do? Mmh.. you can hunt mobs. Old style grinding! Sandbox? Not really. Killing mobs in WoW is like a quantum fluctuation in real life. For a short time you can remove the mob from the world and then BÄM. There it is again. It is like removing a corn of sand, and a few moment later the corn respawns where it was and always will be.
Sometimes 'sandbox' is confused with 'emergent gameplay'. After all you can contact a few buddies, go to Stormwind, pick some guys on the way and kill some peoples' characters. Yeah. I agree that WoW offers a bit of emergent gameplay. Blizzard couldn't completely stop players from doing something else than collecting loot in instances. But while emergent gameplay may be something typically associated with sandboxes, it actually doesn't even require any sand. So, emergent gameplay is great, but, on its own, doesn't make a game a sandbox.
What else? Let me think.
In WoW you can create a guild. By creating and shaping guilds, players in WoW can shape their community. So the box allows the players to not only be inside, but also create relationships. That is not too bad unless, unless.. every MMO I have ever known allows you to create guilds! And, sandbox? Well, where's the sand in that?
Recently people came up with a new type of sandbox gameplay: Phasing. You have an influence on the world! You kill that guy and the world changes. Now.. that is hard. Because, because .. this is some kind of phantom sand. Sand that can be rearranged, but only by you and if you do it, the changes are only visible to you. Look, the point about a sandbox is not that you can rearrange the sand on your monitor, but on other peoples' monitors. And that is exactly what phasing doesn't do.
What if we ignore quests? Wouldn't WoW be a sandbox if nobody told you what to do? Well, no. Look, sandbox means "box with sand". It doesn't mean that there's nothing to do. In fact, most games that are referred to as sandbox have quests, sometimes called missions. The difference between a sandbox and a themepark is not that the sandbox doesn't offer you something to do, but that you can reshape the sand in the sandbox. Try moving that water track over there in a themepark. Doesn't work. Guided gameplay is usually associated with themeparks and unguided is associated with sandboxes, but that's really not the difference between the two.
So is WoW a sandbox? Now, that really depends on what a sandbox is. I mean, metaphorically spoken WoW is a box. I agree. I also agree that there might be sand. Unfortunately this sand has been submerged in some kind of gluten. You cannot change the shape of the sand! It is all fixed! All you can do is change yourself or shape the social relationships of the various players in the box.
Now, changing your character can be fun. Quite obviously it is fun for millions of players! But that is just not a sandbox. A sandbox allows you to change the way the sand is arranged. That is why we use sand in sandboxes and not styrofoam. Even though a box filled with styrofoam can be very fun to explore if it is just large enough.
A fantasy sandbox allows you to create castles, declare borders, remove trees, build houses, build ships,..
And, usually a sandbox also allows you to destroy all of that, because otherwise all the sand of the box would eventually be used up and there has been something built everywhere. Now, that would look rather terrible and also prevent people from creating new stuff. So the sandbox ceased to a be a sandbox.
I hope the next time you read some blog about how you can remove all content from WoW to make it a sandbox you know better. A sandbox, actually, can offer a themepark within. Some part made of styrofoam. It doesn't hurt and can even help with accessibility. But there is certainly no such thing like a sandbox without any sand. And removing styrofoam doesn't add any sand.