The 'missing content' is not some silver bullet set of items on a to-do list. The missing content is more the fabric that links everything together.
1. Combat. Was fubar. Devs are making strides to unscrew it. Great. This is a mechanics correction, not a content creation. But if they get this done correctly, it's a pretty huge step. Combat is merely a means to an end, not the end itself. Combat settles conflict, but the conflict itself should be primarily driven by political and economic concerns.
2. Crafting. You craft to craft. While there is a lot of 'content' here, it's pretty pointless because there is really very little value associated with it. Because...
3. Resources. The world is oversaturated with resources. There is no rarity, thus there is no value. Without value there is no economy. There is very little we can't get for ourselves. There is very little reason to engage in trade, or warfare, to obtain resources.
4. Skills. Everyone can be everything, so there is no value on the individual crafter. IF i want to be something, i just have to grind it...this wouldnt be that bad except, i suffer no consequence for doing this. Game design where everyone can be everything is...bad design...If everyone can be a master crafter, on everything...meh. bad.
5. Accountability. Even if everything stated previously is addressed to a satisfactory degree, it's all pointless if there is not some degree of player accountability. The ability too hold a player accountable for their actions is paramount to the larger game. Accountability is the glue that holds the pieces together...you can't have politics without it. Your economy will stagnate without it (if you control/monopolize a resource 'we' need to be able to make a decision if we want to tolerate that...which in large part will be dictated by the controllers actions). Very simply, without accountability, every gameplay item is really artificial...the moment you make players accountable for each and every action is when you start to see real drama unfold, as players seek to protect and expand their interests.
so while the game is a sandbox [insert meaning], and yes, the players ultimately should determine what happens in it, the game design should assist by channeling players to some type of crucible that serves to ignite gameplay.