There is a meme that is doing the rounds of the mainstream pundits that Helen did it tough when she first took over as leader of Labour so that elevates Shearer's poor performance to date.
Helen faced a misogynistic old boys club inside the Party and in the media. Her issues were the harshness of her image, not her inability to articulate policy and not maim herself 25 seconds into an answer. Helen had mastery of all policy and an understanding of the history of the Party.
Shearer on the other hand has been dumped in the deep end by factions working to prevent Cunliffe from winning without any of the institutional memory required not to shoot himself in the foot when talking to journalists.
Combine that with the Pagani's who are desperately tugging the Party to the right and the idea that one can forgive Shearer's invisible profile because Helen did it tough are a false comparison.