I understand the 'fallacy fallacy' to occur when (a) an argument is criticised and dismissed as fallacious but when (b) the argument on which the criticism is based is itself fallacious.
This doesn't - and can't - make logic useless. We need to use logic to detect the fallacy in the fallacious criticism. Put the point this way. If I make an argument, and you criticise it as fallacious, how could I show that your criticism is fallacious without using logic to find the error in your argument ?
To take an example from the history of philosophy. Descartes is often represented as arguing for the reliablilty of clear and distinct ideas by using clear and distinct ideas to prove the existence of a perfect and therefore veracious God who guarantees the reliability of his clear and distinct ideas. This argument is widely criticised as fallacious (because circular) but if there is a logically valid defence of Descartes' argument and Descartes can solve the problem of circularity, then the criticism (or this particular criticism) that it is fallacious is itself fallacious.
In Med. III, before Descartes proves ('proves') the existence of God he states that :
Whatever is revealed to me by the natural light - for example that from the fact that I am doubting it follows that I exist, and so on - cannot in any way be open to doubt. (J. Cottingham et al., The Philosophical Writings of Descartes, II, Cambridge : CUP, 2008 : 27.)
Clear and distinct ideas precisely are revealed by the natural light, and so Descartes can without circularity use them to 'prove' the existence of a perfect and therefore veracious God. Such a God does guarantee the reliability of our clear and distinct ideas but Descartes already 'knew' their reliability courtesy of the natural light.
Problems of exegesis of course arise. I am not offering this as a full and nuanced statement of Descartes's account of clear and distinct ideas, the natural light, and God. I am simply trying to illustrate how it might be that Descartes is charged with a fallacy of circularity in his argument but that this charge is itself fallacious because its conclusion that Descartes's argument is circular rests on the false inference that the uncertainty about all his ideas flagged up in Med. I still applies to the premises by which Descartes 'proves' the existence of a perfect and therefore veracious God in Med. III. It does not apply, since
'Whatever is revealed to me by the natural light - for example that from the fact that I am doubting it follows that I exist, and so on - cannot in any way be open to doubt.' Those are the ideas Descartes uses in his Med. III argument for the existence of God; in Med. III he does not use arguments open to Med. I doubt to 'prove' the existence of a God who, qua perfect and veracious, removes the doubt to which his ideas are still subject. He uses ideas 'revealed by the natural light' which are immune from doubt.
Samuel C. Rickless, 'The Cartesian Fallacy Fallacy', Noûs, Vol. 39, No. 2 (Jun., 2005), pp. 309-336.