Actually, propaganda specifically benefits (or is intended to) the originating or amplifying entity.
The etymology highlights this:
1718, “committee of cardinals in charge of Catholic missionary work,” short for Congregatio de Propaganda Fide “congregation for propagating the faith,” a committee of cardinals established 1622 by Gregory XV to supervise foreign missions. The word is properly the ablative fem. gerundive of Latin propagare (see propagation). Hence, “any movement to propagate some practice or ideology” (1790). Modern political sense dates from World War I, not originally pejorative. Meaning “material or information propagated to advance a cause, etc.” is from 1929.
The modern definition:
information that is spread for the purpose of promoting some cause.
Additionally, propaganda need not be false. The defining character is promotion and not falseness, though it very often is deceptive in at least some means, whether through the lies of commission, omission, or distraction.
Otherwise, what you seem to be discussing are various forms of untruthful information. There’s a range of these: disinformation (false, though possibly unwittingly), misinformation (intentional), bullshit (disregard for truth, see Frankfurt), misattribution (true fact A mislabled, accidentally or intentionally, as B), myths, urban legends, folklore, trolling, jokes, and even just entertainment and fiction (often rebranded).
There’s also a strong element of psychology involved. Propaganda would be ineffective if it didn’t tie into hooks of emotion, engagement, novelty, simplicity, extant tropes, tribalism, and the like. And those can, on their own, give rise to similar memes and myths.
Propaganda, though, is the deliberate harnessing of these and other dynamics to a specific purpose and cause. As such, it requires some element of control: curation, development, strategy, amplification, targeting, assessment.