It wasn't dumb broke it literally was walled by Amoongus and Celebi. If it drops, Primarina is also a solid answer to it, as well as Starmie, Tentacruel, and can be offensively pressured by Terrakion, Zeraora, Mega Manecetric, Latias, Primarina ONCE MORE, and the ever so popular during tours Jellicent. When It drops, Keldeo will be a nice addition to the UU tier.
Edit:
252 SpA Choice Specs Keldeo Icy Wind vs. 0 HP / 4 SpD Celebi: 180-212 (52.7 - 62.1%) -- 99.6% chance to 2HKO after Leftovers recovery
252 SpA Choice Specs Keldeo Icy Wind vs. 252 HP / 72+ SpD Amoonguss: 180-214 (41.6 - 49.5%) -- guaranteed 3HKO after Black Sludge recovery
252 SpA Choice Specs Keldeo Hydro Pump vs. 252 HP / 4 SpD Primarina: 117-138 (32.1 - 37.9%) -- 0.9% chance to 3HKO after Leftovers recovery
Alright, Celebi not as much, but its very punishable if they click icy wind and lock themselves into it because then you can just settup with Zor in their face. So yea, it may be annoying to switch into, but so is Terrakion and it's doing fine (for now). Primarina proves itself a hard counter once more.