User blog comment:HarmonyBass/Destiny Ramblings: The Vex and why they haven't won yet. (WARNING! MIGHT GIVE YOU A HEADACHE!)/@comment-160529-20170604025049

I want to add further, if the player character is indeed Dr. Shim... then it could explain why The Player guardian is so important. As Dr. Shim was able to overcome the Vex's attempt at torturing their mind and was able to recognize that... to himself, it didnt matter if they themself were simulation.

and that perhaps this is why The Guardian is so important to the defeat of the Vex... and while the Vex are not the Nemesis of the traveler and the guardians (the darkness/hive is) they represent an uncaring threat to all things.