Jaya may not be the most powerful planeswalker in the set, but all three of her abilities are super well synergized. Her second ability works especially well with the Hollow One and Drake Haven decks in Standard.
As for Modern, once again it's a perfect fit for the Storm decks. And if the game goes on for too long, then her ultimate ability will perform wonders when casting spells from your graveyard. But that's basically it!
Among all the planeswalkers in Dominaria, Jaya will be the least valuable one for sure.