> Taibbi, himself a left-leaning journalist (formerly at Rolling Stone)
Yes, he's the type of 'left-leaning' person who described a book about white privilege as "Hitlerian race theory" and wokeness as "mak[ing] the Junior Anti-Sex League seem like Led Zeppelin" [2], and also described not only what you (and he) call 'Russiagate', but the Ukraine incident as well, as a "permanent coup" [3] where Democrats' conduct was more corrupt than the conduct being investigated. Sure. I guess you could call it 'alt-left'.
> has catalogued these at length on his substack.
If there's a full list of supposedly false "bombshells", it's not publicly available at that link. But it's strange that its lead example is the Times' exposé of Trump's taxes, which even it admits is "real information" that suggests "potentially real" tax fraud (plus Trump not being as wealthy as claimed, what a surprise). Should it not be news that the Times found what Trump had been going out of his way to conceal for four years? Because the darkest speculation from the past proved false – speculation by random pundits, mind you (Taibbi doesn't link to anything from the Times, though for all I know there might have been some op-ed by someone) – does that make Times' report somehow fraudulent?
> In the cold light of the morning after, even WaPo has criticized the coverage over stories sources from the Steele Dossier
Rachel Maddow is a terrible journalist who makes exaggerated claims about all sorts of things. I wish she was not on the air, and Erik Wemple of the Washington Post was right to criticize her. But she is not representative of "the media"; she is rather unusual as left-leaning TV figures go. (Her "less degreed critics" on Fox News are far worse.)
But you didn't link to the Washington Post article. You linked to a Mercury News article that briefly mentions it. The Mercury News article, however, is full of misinformation. For example, it claims that Mueller investigation found "no evidence of actionable Trump obstruction". Well, technically, yes – because it assumed it could not indict a sitting president under any circumstances. The report suggested that the behavior would have been indictable otherwise, though it officially did not make a determination one way or the other.
[1] https://taibbi.substack.com/p/on-white-fragility
[2] https://taibbi.substack.com/p/if-its-not-cancel-culture-what...
[3] https://taibbi.substack.com/p/were-in-a-permanent-coup