I think what you're lacking is a campaign. In theory you can make a sandbox world with randomized quests or staged events. That's basically what Terraria was until the later updates. Without a story, the player engages with a sense of progression and mastery. Going through the crafting tier material lists. Copper >>> Adamantium.
The Diablo games also work like this, but they have an accompanying story. You go to locations for story reasons.
I think it would be a challenge in itself to try to write an adaption for Terraria that explains the end game progression. A "why" You need to defeat Plantera to get a key, to defeat the temple golem, after which the cultist show up, after which alien invaders show up, and then the Moon Lord. What's the narrative thread stringing this all together? Why does throwing the Guide's Voodoo doll into lava summon the wall of flesh? What is the point of all this?
The problem is trying to get to an end of something that doesn't have a point, or an end. There was a writingexcuses podcast about serial storytelling and how to conclude something that is structurally endless. And their advice is to close on an emotional beat.
Because you might be writing a Saga or Chronical or something. In reality, their story wouldn't end until a kingdom falls or a character dies.
In practice, the story ends when the narrator/chronical/scribe/bard puts down the pen or can't follow any further. You know, like if the story was about an eternally damned Vampire trying to redeemed it's soul. The story wouldn't end with their ideal salvation. The opportunity might have come up, but they would probably sacrifice it for the B-plot companion to find happiness or something.
The most relevant personal experience I've had with this is a collaboration project I wrote an ending for. Now, because it was a collaboration, there were a dozen other developers who wrote "chapters" introducing new characters and starting plot threads that the next collaborator would just plain ignore and not follow through with. (So it was hardly a collaboration). Understand, I was ending something that never really began.
Like the prologue mentioned portals of darkness and 5 chapters later, we never saw any portals.
It was bad. I think, what was suppose to be a darkness generator disguised as a smoking volcano ended up being an actual volcano. It kind of worked, in theory we could have visited all elemental dungeons. but then nobody picked it up again for the rest of the year.
And we had agreed that the collab would end at the end of the year.
All I remember, is that the party was stuck in a Volcano for no good reason except to use the fire cave tileset, and no way out because it wasn't even explained how they got in there. They fell in or something.
If I remember correctly, I had an evil alchemist show up and haul everyone back to their castle lair of darkness. Where the player had to fight corrupted versions of the party members. I think they ended up destroying the source of magic or something vital. Everything went to shit, everyone hated each other, and I'm pretty sure I ended on a line "We can start over if we collaborate". :shades: