Funny that this effectively counters the uncounterable dovin's veto.
If I break this down into a few modes, it has a mission briefing like buyback your spell effect when not interacting with opponents on the stack, it is extremely good for defending your instants and sorceries against counters and your removal against dive down by buying back the original spell that was in line to be countered or fizzled and resolving it anyway, it is an answer to the uncounterable dovin's veto in control counter wars, it has a remand like tempo element that is especially potent against opposing resource generating spells like Chemister's Insight, Circuitous Route, or Nexus of Fate (people mentioned the interaction with Nexus of Fate earlier, but this is an amazing counter against a Nexus of Fate, stranding it in their hand and time walking them), or against targeted removal, buying your permanent a turn and destroying an opposing permanent in many cases. It is probably at worst a hard counter against Thought Erasure or Duress, giving you the option to remove the countered discard spell from the opposing hand or take a more important spell. Flashback and Jump Start spells cast from the graveyard get exiled if removed from the stack, so this is a hard counter and copy for something jump started, very relevant on the aforementioned chemister's insight's backside.
Those all seem super solid for UU. Might end up only being a sideboard card, since most of these are applications in control mirrors where stack interaction is heavily emphasized, but I could also see this being a super strong weapon in the arsenal of monoU against targeted creature removal from midrange decks.
A planeswalker wrath was an inevitable safety valve of the walker set. Giving your opponent the initiative by having them have the next turn where a creature or walker can be played kinda sucks. It is an interesting pairing with the amass mechanic which is going to voltron together a giant army creature.