OHKO moves aren't banned because of the environment, they are banned because they allow the user to win battles on luck alone. Pokemon's oldest and most glaring inherent flaw is hax; the amount of hax in a game is inversely proportional to that game's competitive quality. "Competitive pokemon" is already enough of an oxymoron without double team and OHKO present, especially with no guard dudes running around.
Jirachi's flinch chance isn't remotely comparable to a move that kills your guy in one hit. Jirachi is easily checked. The only thing you can do against Sheer Cold is pray that it misses, which is the exact opposite of what you should be doing in any competitive environment.
Jirachi's flinch chance isn't remotely comparable to a move that kills your guy in one hit. Jirachi is easily checked. The only thing you can do against Sheer Cold is pray that it misses, which is the exact opposite of what you should be doing in any competitive environment.