Vex would go back in time to prevent his birth. Immortal Hive Gods that can destroy planets, and Goku needs an atmosphere to survive. He isn't Superman. Cabal would blow up the planet. Vex would destroy the fabric of reality. The Darkness is pretty powerful. If Goku entered any Vex underworld, he'd be written out of reality and time. Not to mention Crota is immune to all forms of damage, since he's a God. He can only be brought down with an Ascendant Sword, not a regular Hive Sword. The Vault of Glass can't be destroyed. It's on Venus, but it's also not. It exists in between the Vex dimension and ours. Goku would need to enter. He'd blow open the door, and bam he no longer exists. No one will remember who he is. Goku can destroy planets. Goku is a God. Goku can beat anyone. That's all whiny fanboy nonsense. Goku can, but he won't. Goku can, but he chooses not to. Goku can can can, but he will not. All these super fanboys of Goku, and they're saying what he can do, instead of what he will do. He will not destroy a planet, especially if there's life on it. He cannot destroy the Vault, as it will still exist. Forever. He could kill Atheon, but only in that one instance of time. Atheon exists in all times at once. Gorgons. Kill 2, the rest become invincible. He can't kill them, and they'll wipe him out of history.