Emma Handy said it all right here last week, so I wont spend too much time repeating her argument in detail, but to quickly recap: Vivien, Monsters Advocate compares favorably to current top-tier green planeswalkers like Vivien, Arkbow Ranger and Nissa, Who Shakes the World
Since Palinchron untaps up to seven of your lands, you can then use four of that mana to return it to your hand with its activated ability and play it again to make an infinite number of tokens and infinite mana
This card will most likely be a sideboard piece, but it can have great value against a planeswalker-heavy opponent
If the one-mana cantrips were around, combo would be even more consistent and, because of this consistency, probably a bit faster as well, which would push decks toward playing or splashing blue, just for the power of Preordain and Ponder, and the diversity we see today would be greatly diminished