If Shanks knew exactly what the fruit was, then why wouldn't he have told Luffy what it was instead of calling it the Gum Gum Fruit? And why did he still tell Luffy he was a Faggot until Luffy outright declared he would be Pirate King if he Knew (because the Fruit Chose him) that Luffy was the chosen one?
And if Shanks didn’t know what the fruit really was, why did he steal it in the first place?
Also, the reason Shanks gave Luffy so much shit is because Luffy was adamant about joining the Red Hair Pirates, no matter how many times Shanks said no.
Luffy won't be a chosen one...because some predetermined destiny is the polar opposite of one of Luffy's goals
"To be the freest man in the world"
That implies Luffy cares about a destiny that chose him. So you may be right for the wrong reasons.
It took when Luffy reached Gear 5 to learn who Joy Boy was back when Robin asked about him at Fishman Island, along with figuring out who Nika is after Who’s Who first brought it up. And it was also that moment when we learned that Luffy’s devil fruit is connected to a sun god, and the Gorosei have tried and failed to get a hold of it since the Void Century, like the fruit has a mind of its own (their claims).
It’s very increasingly clear there’s a process Oda is following:
1. Lore drops.
2. Character explains how a character will do something relating to that lore.
3. Luffy does something.
4. Character who knows more than the Straw Hats explains how Luffy relates to point 1 and how his actions satisfies point 2.
If Luffy does have a destiny, then it’s going to be fulfilled in a roundabout way because he’s got his head in the clouds doing his own things and can’t be bothered about some stupid prophecy, if he even learns about it.
It’d be like if Lord of The Rings started with Frodo just being told “hey, here’s a ring. Go to this mountain and throw it in there.”, told absolutely nothing else, and Gandalf, Legolas, the non Hobbit members of the Fellowship and several others are providing commentary on Frodo’s journey in regards to how it’ll shape the future of Middle Earth.
It’s like the universe has to convulse and bend itself to get to a certain point in order to reach a certain outcome because Luffy is the one, but Luffy is such a dense motherfucker with a carefree attitude that it’s a pain in the ass to keep up with him and his antics.