WikiLeak's big coup was cablegate, the main revelations of which boil down to "diplomats are very frank about people when they're not speaking in public." At the same time, Assange seemed to want it to be compared to the Pentagon Papers leak, which revealed that the US military was covering up the course of the Vietnam War. Instead cablegate was a whole lot of quantity over quality, and don't really merit the comparison.
Since then, WikiLeaks has missed out on the big revelations: Snowden's releases, the Panama Papers and Paradise Papers, as well as more regionally important leaks such as Lava Jato. There's no trust among leakers that WikiLeaks is a neutral source for divulging information, and the fact that Assange has seemed to have a specifically anti-US tilt which results in him getting cozy with anti-US anti-press-freedom regimes.