Who says they haven't tried?? Dinklebot said that The Traveller played a key role in stopping the Vex. We don't know exactly what was done. Or---for that matter---even what the goals of the Vex are.

True. Examining the grimoire cards it looks like the Vex want to somehow exist outside of reality but have the ability to interact with it. Maybe? Who knows, maybe they're trying to validate their existence and prove that the real vex aren't a simulation. As to the Traveler, who knows what it did to keep the Vex at bay. I'm just curious as why it's taking them so long to terraform Venus. With the Traveler unconscious they could have done anything to the planet. Looking forward to an explanation.

Probably because they don't have the power to do so. Here's my take: The Vex only have power over TIME and information. They don't have the power to CREATE anything new. Especiallly where LIFe is concerned (The Hive have power over Death and Destruction). Of all the entities that have appeared in the Destiny Universe, only The Traveller appears to have the power to create new things, and to defy the laws of pHysics n the process. So without the Traverller in play, the Vex only (theoretically) have the power to turn Venus inot some sort of massive computer. But only the Traveller could "terraform it....

Me too! Now that they have finally hired a new head writer we may get an answer to that.