Luffy is portrayed as the central underdog through most of the story, arguably he’s never not been the underdog in most arcs he’s in.
despite inherenting CoC, befriending a celestial dragon Yonko, having two legendary relatives in Garp and dragon, Ace too technically.
he’s an underdog with every advantage including a mythical zoan fruit with its own will that he ate as a child.
Naruto was portrayed as an outcast that won over most of his peers by the end of part 1 & that theme isn’t really hard addressed again until the Pein arc. Woulda been nice sure but the focus of the story drifted from Naruto’s loneliness and struggle to Naruto’s bond with Sasuke
Again, it's about the contrast.
Naruto was portrayed as an underdog + talentless + failure in comparison to his peers who had talents due to Lineage.
He was portrayed as someone who has grit to work hard to overcome lack of innate talent due to fate or lineage and will create his own destiny.
First few arcs of Naruto was gold because of this.
So when we got all those lineage and destiny stuff later on, it just ruined entire Naruto character because he always had lineage and fate working for him like others. Infact, way more than others.
Luffy did get portray as underdog but not in comparison to his peers (he literally shits on them - kidd, urogue, bonney and so on). His underdog persona kicked in against villains.
And then Luffy was always portrayed as talented, someone who can achieve which no one did. We began one piece with Shanks entrusting strawhat to Luffy and Luffy calling himself strong. He had that bravdo feel about himself from the get go. So when later on lineage came into picture, people were like "oh that explains his bottomless will power".
One piece has it's retcon moments but it never really deviated from it's core theme around MC and manga. Naruto did.
Infact, most of the disappointments of one piece is due to haki and PL inconsistencies + oda build the world so massively that by the time an end of an arc nears, he hardly do justice to all the sub plots he laid ..
One piece theme and story have always being going linear. In case of Naruto, core theme in itself got 180 degree turn along with other stuffs which didn't go well with readers.