Unfortunately, it seems recently most of the time juries are not informed of their nullification abilities (and the defense is often prohibited from mentioning it). Sadly this line of reasoning has been upheld in court.

They didn't "establish nullification" - nullification is simply the logical outcome that the jury's decision is final, and can't be questioned.

The reason judges don't want this fact brought up by counsel during court is because it would render the legal system meaningless... in general I think we'd all LIKE the jury focused on the law and the evidence, not their gut feelings.

This always comes up in discussions when we feel the law is unjust and the accused isn't getting a fair trial - but please consider, if counsel were allowed to bring this up in court and instruct the jury that, you know, regardless of what you have heard here, you can vote however you feel like it and, you know, nobody is allowed to give you shit over it afterwards.... that street runs both ways. You'd have people who DO deserve punishment getting off scott free.

It wouldn't render the legal system meaningless. It would return verdicts according to your 12 peers. Jury Nullification is not about using your gut feelings its used for when the application of the law would return an unjust or immoral result. There is in my estimation, no better judge of the law than 12 of your peers.