Being a leader is the same as being a Unifier, the only times you mention she worked with a preestablished group that would have been on the same team without her.
Also Navani did nothing for discovering Urithiru that was mostly Jasnah.
Anyone who isn't exemplary is unworthy,
Think about it this way, if I had bondsmith powers I could take your connections to everyone you know, for all intents and purposes I would become you to them, they would have no special connection to you. To even your closest friends and family you would be no more than a stranger they would feel nothing towards you. Your friends wouldn't look twice in your direction, I would uterly and totally replace you in their lives, and there would be nothing you could do about it. Now tell me, who do you think should have that kind of power?
Journey before Destination, the important thing is that he tried.
When does she manage to get people who wouldn't work together to do so? You can't even say Raboniel since it was Raboniel, not Navani that made that situation work.
Restoring the Siblings Rhythm of LIght isn't good enough, and on Rlain, even if it doesn't come naturally to him he does it, that's the important thing, he tries.
She's smart but she didn't discover it, it wasn't even a close thing Gavilar had it almost eight years before she did.