On one, its a very efficient token generator for aggressive decks, applying a ton of pressure early and synergizing with a lot of different cards
The fact that it has a weird keyword and it was reprinted in a recent Masters set means that it could dodge another go-round for a few years, and Extirpate is one of those solid but unspectacular sideboard cards that sees enough play to maintain a fairly high floor
Sure, it may only be half the card drawing of something like, say, Mulldrifter
Sure, even Liliana would have to approve of that power upgrade
It's made all the better by having a flying body that gets bigger as you cast bigger spells, leading you to incidental Voltron wins as you plop down small mana rocks to get to huge mana rocks to get to huge Eldrazi titans
Gyarados has one of the highest HP points in the game and it only costs one evolution to make him tanky