That said, I think there is space to debate what the boundaries of that ought to be, and I think there are too many state secrets in the United States.
The concern is that Assange has turned WikiLeaks into his own personal intelligence agency to achieve his political goals. And these WikiLeaks-leaks from the past few years seem to confirm much of that concern. Assange constantly uses language in these DMs indicating intent to influence political situations to his favor, and the subtle and nuanced ways they can affect and control narratives.
I'm not really convinced Assange and WikiLeaks are puppets of the Russian government, but I do think Assange has let the power and prestige go to his head, and has now rejected any pretense of neutrality and humanitarianism. WikiLeaks is now Assange's personal machine to change global geopolitics in a direction he likes; nothing more. Who knows if that was his intent from the start or if it's a case of "die a hero or live along enough to see yourself become the villain". They should really change their name, either way.
And WL is absolutely part of the media.
As for the 'reasonably general conception of the public interest' of wikileaks, I suppose it is 'to get all of the truth out'.