Haze Quagsire is and always was utter crap and was nothing more than a terrible gimmick. It was used on full stall teams to stop set up sweepers (as KD stated already). Nowadays full stall isn't good in the meta anymore, and being as passive as Quaggy is just doesn't cut it. People went for other options such as Mew or Cresselia to stop set up sweepers, or sometimes even Clefable as Clefable actually packs some offensive presence.