So reality is not just in Shonen or even manga, but in majority of main stream fiction the heros are there to win in the end and if you hate that then its best not to be fans of any hero. And that happens because historical purpose of creation of fiction was to bring joy to people, victory isn't guaranteed in real life but when someone suspends their disbelief for fiction they are in a sense taking a break from troubles of real life.
Zoro's character is relatable because we see his trials and tribulations, we have clear account of his motivations, where his overwhelming desire to achieve his goal comes from, the promise to his friend, we see him start out as a no body and bust his ass day in and day out. What Zoro does aka bust your ass towards the goal, work hard and work smart is a way to success and of course success isn't guaranteed but that's where Zoro being a hero comes in the play, he's there to give positive perspective and motivate.
Luffy is the same but problem with Luffy is his trials and tribulations feel shallow, his motivations are vague, he has no Kuina, he wants to be Pirate King just cuz, his definition of freest man on seas is Wonky, he will end up being pirate Jesus something he didn't even work his entire life towards unlike Zoro.
Yeah of course Kidd will fail because he's a side character, he's there to enhance the story not to be the story. Zoro and Luffy don't move the plot they are the plot, story revolves around them so of course when story ends they will win.