Criticism that doesn't lead to action should be ignored. But, criticism that is backed by action should be harnessed.
This means that as a leader, you can disregard the person's complaints who also isn't showing up at meetings, paying dues, volunteering, recruiting, or suggesting a better path. That person isn't committed to the organization and is only using it as a punching bag.
But embrace the person who critiques the actions of the group and then offers other ways to do it better, who is actively building a membership base, or who is helping to raise funds. They have skin in the game, a stake in the outcome, and really want things to be better. They criticize because they care.
And the same goes for you as a follower. If you're not willing to work to make things better, don't merely throw stones at those trying to build something. If you're not willing to work to improve something, maybe your heart's not really in it and it's time you found something you'd enjoy more.