I hear what you're saying, but it's clearly at odds with the position described at https://www.aclu.org/blog/speakeasy/heller-decision-and-seco... .
They explicitly interpret 2A as a "collective right," whatever that is. They also state their disagreement with Heller and presumably any number of lower court decisions in line with it.
Organizations like the EFF never claimed to be broad-based "civil liberties unions," so that's why I feel it's appropriate to hold them to different standards.
However, they never argue in court against 2A. Nor do they prohibit their member state organizations from taking a different position - and many do.
Yes, ACLU is a broad "civil liberties" organization. But there's no definitive list of civil liberties, and different people have different opinions on this. The fact that SCOTUS ruled on it doesn't change matters - SCOTUS rules on whether something is a constitutional right or not, not on whether something is a civil right or not. The latter is inherently a subjective assessment.
They're also upfront about this position, so you can't claim that they're misleading you when they take your money.
When you donate money to ACLU, you do so in the knowledge that not go towards defending 2A rights[1]. But this is also the case for EFF, for example. Does that preclude you from donating to EFF, or any other organization? If not, then why do you demand that ACLU does something out of their declared scope.
[1] ACLU does actually defend 2A rights in contexts where they intersect with other rights. For example, they have collaborated with SAF to defend the rights of non-citizens to keep and bear arms - some states explicitly ban non-citizens from their shall-issue carry licensing provisions, or even firearm possession in general.