Anonymous sources are a different thing altogether.
They are generally giving out specific facts.
Yes, of course those things are generally about manipulations of some kind, but there are protocols involved, and those 'anon facts' generally have to be true. In these situations, the news organizations credibility is on the line. The more credible the entity, the more likely they've done their checking/double checking to corroborate etc..
Many legit stories break this way.
Again, yes, it's all about narrative ... but there's generally more meat to the narrative in those cases.
Tweets by individuals who are authoritative on something are also a different thing. If an actress says 'I faced harassment from several studio execs' - then this has some credibility as a statement.
But this is altogether different from the straw-man 'people are saying' types of stories which are very common. A daily occurrence.
The 'materially useful' tweets are a small thing.