When I try to create a world after setting up my custom structure, it crashes

So, I'm creating a world type that'll just be one island. The way I'm going about this is with a massive island structure. The file type is correct, it is .NBT. However, whenever I try to load the world ever since I did stuff like put the .NBT file in the datapack and create a json for the island structure, trying to create a new world always causes the game to crash. What could be the reason for this? Could it be that the structure is too large?