Does the game have a real focus or clear goal? Yes and no... You can simply wander around the game, find objects, interact with them, and delve deeper into the game's mechanics and world. I'm probably more focused on giving meaning to various objects and their interactions than on creating goals. Every object in the game should serve a purpose. For example, what is this plant? The player uncovers the plant's meaning, and what is the resulting result for? And so on. You can create your own goals, you can stumble upon objects that give meaning to the game, or you can simply find missions with a clear goal and accept them or ignore them. But at the same time, there are already simple tasks and complex missions whose completion formally ends the game. Generally speaking, the sandbox genre itself doesn't have a clear goal.
As for mixed genres, embodying all the features of the listed genres in a single project is undoubtedly not an easy task, so these will likely be partial elements of the genres, and only if they help deepen the world, imbuing it with new meaning and dimensions.
For example, I was developing a hierarchical skill system and character stats, but I had to stop that section and make a simplified version because the full-fledged crafting system hasn't been finalized yet, and it's unclear whether the game as a whole is engaging for players.