I've never played it, so I really can't speak to the though, but my obvious comparison is Minecraft.

I really think the deep lore of Minecraft does a lot of work. When you find a new and interesting random place to explore, it usually ties in with your view of the place you are in, and eventually you find your way to an ending of sorts.

Another similar game from my youth that was the same was Wing Commander: Privateer. It was a sandbox, where a game suddenly appears after you've been exploring for months, but it's not much more than some cut scenes within the sandbox.

I have no qualms with a sandbox game, but I'd prefer it were generally tied into a narrative, either in a lore narrative or with a direct story.