Kid and Law both fall under the general shonen stock rival archetype. Everyone knows the hero will end up overshadowing them but it’s up to the author to keep them interesting until then.
Kid failed miserably. Kid needed to be an arc antagonist to overcome to be taken seriously. That’s what his entire pre-skip schtick was
-he had a higher bounty than Luffy, making him top of the Supernova
-he even had a Supernova under his command, same as Luffy, and Killer’s bounty was higher than Zoro.
Kid and Killer needed to be fought with by Luffy and Zoro when the respective bounties favoured Kid and Killer, so our heroes seemed like underdogs. And those fights would have needed to have ended with the two opponents on a relatively level peg. Extreme diff, very balanced but unfinished, straight draw, something like that.
Instead in Kid‘s first proper arc we already went in with Luffy shitting all over him. Luffy was the 1.5 billion Fifth Emperor FS wielding man who had beaten Katakuri, the strongest The greatest thing we learned about Kid was that he had CoC and had wounded a SC who was not Katakuri.
Then comes the fights in Wano and Luffy absolutely shits all over Kid. Like, not even close. Luffy‘s crew shits all over Kid’s. Again, not even close. Luffy genuinely should be able to solo the entire Kid Pirates. And it’s not like we got much from Kid character wise to make him interesting either.
Kid’s the archetypal rival to be surpassed… who got surpassed by Luffy before Kid even had a real role in the series, and in his first real arc the gap was only blown even wider. The idiotic equal bounties did nothing to remedy that. Your Vegeta’s and Sasuke’s worked because to begin with they were genuinely stronger or equal to Goku and Naruto, proven in fights. Luffy and Kid have never fought and they don’t even need to because Wano’s made it clear that Luffy shits on him.
Law was a bit different from the beginning. He had the lower bounty (by quite a bit) and then he saved Luffy in Marineford. Doesn’t have a Zoro/Killer either. That’s early setup for him to be an ally instead of a rival, confirmed in PH and Dressrosa. But since then he’s been meandering along in the sidelines for Zou, offpanelled in WCI, pretty much did nothing up until Roof Piece, 100 chapters into Wano. Kid brought out this retarded insecurity about being Luffy’s sidekick and his goal is literally just Robin’s. We’re never going to take him seriously as any sort of rival to Luffy, again, the equal bounties were just stupid when Luffy so clearly surpasses him and going forward there’s just not much reason to care about him. At least unlike Kid, he did have a time where he had something interesting about him, but that was finished in Dressrosa.