#IDK I see people often kind of just. Overly simplify (/dumbify) One Piece's themes about family into just like

[moongothic]

You know we all meme about how Luffy doesn't give a shit about his parents/Dragon, how he seemingly has no interest in learning about the man or meeting him at all, and like yeah that is a Luffyism

And for a long time I figured Baby Luffy would be the same too; that Luffy in his naïvete just accepted he must've spawned from the ocean itself into Garp's care or something, not realizing he should in fact have parents, thus Luffy's seeming disinterest in them

But you know what

Luffy did spend most of his early childhood alone

Sure, he had Garp, but it seems like Garp wasn't always there to look after him every day, he had his duties as a Marine too. Had Garp been there 24/7 all year then Garp would never have allowed Luffy to interact with Shanks (a filthy pirate) to begin with. So yes, Luffy had his grandpa, but not all the time. And sure, Luffy also had Shanks, but Shanks didn't spend all his time in Fuusha Village either, he came and went whenever he pleased too until his final departure when Luffy was just six years old. And yes, there was everyone else in the village too, people who cared about Luffy and were helping look after him. But Luffy's early childhood was one without a stable family.

It wasn't until Garp yeeted the child into Dadan's care that Luffy actually gained a proper family, where after months and months of trying Luffy managed to win Ace's trust and gained Sabo as a brother too. But as we know, by that point Luffy already hated being alone

All of this to say; Luffy growing up essentially orphaned would explain why he's so afraid to be alone, the way he clings onto people

In some ways Luffy's POV is meant to be the reader's POV, to some degree Luffy's feelings and thoughts are meant to be how we the readers feel and think about whaveter is happening in the story. Not a 100% by any means, but somewhat at the very least.

Perhaps Luffy's lack of interest in Dragon isn't just "Luffy not giving a damn about blood family because chosen families are better" nor "Luffy is too stupid to understand where babies come from". Perhaps Luffy, who may have assumed he didn't have parents at all (as in "might've assumed they were dead or had intentionally abandoned him"), doesn't know what to think about the fact that he does have a father out there, one whom he has never as much as met. Because yeah, Luffy doesn't know why Dragon left him with Garp, why he never got to be with his dad. Should he be angry at Dragon, hate him for being left alone? Or did Dragon have a good reason for it, does Dragon wish things could've been different?

Perhaps Luffy's seeming disinterest in Dragon isn't because he doesn't care about blood family, but because much like us the readers, Luffy doesn't quite know what to make of Dragon, and figuring those feelings out hasn't been relevant to the plot yet.