The Official Glyx
Banned deucer.
Despite being a QB-worthy threat in the DLC1 metagame, the onset of DLC2 brought with it several considerably powerful answers to Jirachi that weren't usable prior, between the likes of Victini, Volcanion, Zygarde, Landorus, Regieleki, Heatran, Moltres-Galar, etc, etc. So many new threats to Jirachi caused it to fly under people's radar for a while as the 1v1 Council had to address the several other threats that became immediately much more prominent, up until the past month or so where a new set came to light that gave Jirachi a full 180-degree turn from being an underwhelming haxor with a neat amount of coverage into one of the most oppressing Pokemon in the metagame, with many even suggesting it was more problematic than Genesect, which was being suspected at the time!
Weakness Policy alongside dual defensive setup moves allowed Jirachi to capitalize on its naturally high speed and defenses, making it into something that was near impossible to KO without the likes of incredibly high power to KO through its boosted defenses or outspeeding it, since Jirachi surviving a super effective hit left it with a tremendous boost to its offenses that only got multiplied exponentially by Stored Power, resulting in a move capable of OHKOing even something as bulky as Zygarde after just 1 turn of setup and WP activation! In addition to all this, Jirachi used the move Encore to make it nigh impossible to stall down or set up against, as well! Coiling with Zygarde becomes a loss, trying to lock it with Choice + Trick just leads to your item being sent right back to you, trying to PP stall it with Zapdos just gets you set up on and eventually KO'd, etc. While Dark types may threaten sets with Stored Power as the only attacking move, it wasn't exactly difficult for Jirachi to just slap on Moonblast over something and flip those matchups to its favor.
While Weakness Policy was plenty strong, it was not without weaknesses; things like Taunt Spectrier, Registeel, and Chansey all gave WP Jirachi issues by either locking it from setting up or bulking it down. However, Weakness Policy was far from the only thing Jirachi was capable of using well, with multiple Choice items serving it nicely, as well as a plethora of other sets between defensive berries, Thunder Wave, etc, all of which made it a lot easier to flip these kinds of matchups in Jirachi's favor. When factoring in the sheer versatility Jirachi had at its disposal, it started to strike similar notes to how Genesect was often capable of teching for just about anything it wanted to, but with the added benefit of having RNG as a fallback even if you pick wrong, in addition to WP on its own being such a domineering threat that people outright had to prepare for. This left true Jirachi answers being limited to the likes of Choice item Volcanion and Heatran, Regieleki, Volcarona, Incineroar, etc.
With counterplay being this limited, or otherwise excessively focused on setguessing, Jirachi simply became too much for the metagame to handle in extremely rapid fashion. With discussions about Jirachi showing near universal support for its removal, the council has held a vote and unanimously agreed to ban Jirachi from the 1v1 metagame!
Tagging Kris for implementation