If you cast it without a Time Vault, you could go find it and threaten to take infinite turns, next turn
Zur is best in a deck with silver bullets like Stony Silence and Deafening Silence that can be quickly found
This card might as well say, "as long as you control a creature, you cannot lose the game." 17
As a result, youre going to have to dig really, really deep to find playable generic mana ramp for mono blue Commander decks, and many of your best ramp options will likely have some form of limitation
Those proportions are the backbone of nearly every consistent EDH deck - enough lands to avoid mana screw, enough ramp and draw to keep the game moving, enough interaction to survive, and a real plan to win