That... not remotely true. No one writes stories for major organizations based only on tweets[1]. Go pick up (figuratively) a newspaper and read the front page stories carefully, and make note of how the sources are identified. I'd be beyond shocked if "twitter" appeared even once.

IMHO the real reason for "collapse in confidence in journalism" is that this is itself a meme driven by people who, for partisan reasons, simply don't want to have confidence in media reporting things "their side" doesn't want to be true. In a world where truth (about climate change, election results, disease impact, etc...) is a partisan thing, those whose job it is to report the truth become part of the war.

But reporters today are doing the same thing reporters have always been doing.

[1] Except the occasional circumstance where someone specific says something notable and it happens to be on twitter. Trump said lots of weird stuff and it got reported, but it's not like someone went around filtering his otherwise-not-notable tweets for juicy stuff. "He Just Tweeted it Out" is a meme for a reason.