Many of you are still missing the main point. To counter Double Team, not only do you have to counter the move, but you also have to counter the potential users of Double Team as well. That means you have to counter 600+ pokemon as well, except now you're limited to using those 60 power moves, Haze, etc.
Countering DT isn't the same as countering BP or Drizzle either, because countering BP and Drizzle is countering a few specific pokemon, not 99% of all pokemon in the game. It's already pretty much impossible to counter 600+ pokemon with a team of 6 even if they don't use Double Team, and then being limited to use a bunch a specific pokemon with anti-DT capabilities and also being limited to use a specific list of moves and abilities only makes it even more impossible.
You can't even say that only the few in their specific tiers matter either. Almost every pokemon in the game can hugely benefit from having attacks miss them, so even UU and RU pokemon have to be taken into consideration as well for OU teams.
Even a team of 6 pokemon using anti-DT things like Haze, Aura Sphere, Unaware, etc. has about the same effectiveness of "countering DT" as just spamming 75 acc attacks and hoping they don't miss, if the opponent manages to use DT.
Arguing that DT can be countered is just wrong, because there will always be dozens, if not hundreds of DT pokemon that outnumber and can beat the specific pokemon that have anti-DT capabilities. The only pro DT argument that's kind of works is saying that having all your attacks' accuracy be that of Sleep Powder or lower isn't so bad, but not really