You do make some valid points but you made it sound like Zoro has no role but to fight in the Crew. My point was Zoro is the unofficial first mate, If Luffy gets incapicated, the leadership role would automatically shift to Zoro.
Luffy normally ask Sanji to cook for him, I have also seen him ask Nami to navigate, not once has he asked Zoro to fight an arc villian for him. Zoro can get strong but I feel as long as he is a crew member of the SHPs, Luffy would always haki bloom his way one step ahead of Zoro by grinding through arc bosses after arc bosses. What exactly is Zoro doing differently than Luffy, training was his thing and now Luffy is starting to train his Haki as well. The only way I can see Zoro truly surpassing Luffy is if he leaves the crew or start fighting the arc bosses which we all know ain't gna happen.
Luffy's initial goal wasn't to be strong till he saw his brother die & saw his crew yeeted across the OP verse. He said that himself.
Mihawk was waiting for someone stronger than Shanks cos Shanks is a swordsman. If Mihawk was really about it and wanted to fight a stronger combatant than Shanks, he woulda walked down to Kaido and challenge him. We all know Kaido loves a challenge.
Ryuma is just built different. Ryuma was the world's strongest man period.
Luffy's Fights are about Dreams & not Strength because the Villains he Fights are mostly Superior than Luffy or way Weaker.
He does fight some of his own Level but it's rare
Zoro does Fight the Most Troublesome Villains & Protected Luffy many times.
Let me give you Examples:
1. Zoro's Introduction Arc ---> Morgan was gonna Attack Luffy but it was Zoro who Finished him off & literally Joined the Crew right after he Saved Luffy from an Attack (I know Luffy can handle Morgan easily, but the symbolism is what matters here)
2. Buggy Arc ---> Luffy was trapped & gonna be Executed by Buggy but Zoro saved him & fought Buggy first. However Oda made Buggy have a DF that counters Zoro, just so that Luffy is the one who fights him. Coincidence? You think it's coincidence that from all the DFs that Oda could have picked, he chose the only one that counters Zoro? It's obvious Oda had to do that to give justification why Luffy fights the Villain & not his Crew Fighter
3. Kuro Arc ---> Luffy was Knocked Out & Nami/Usopp was hiding so it was Zoro's Sole Job to Fight & he handled Nyaban Brothers, but when Kuro came, Kaya also appeared & then Jango went after her, so Luffy ordered Zoro to go protect her & he had to carry Usopp who defeated Jango himself. Which again shows that only reason Oda made Usopp Injured & Unable to walk was to give an excuse for Zoro to leave the Scene & let Luffy fight Kuro
4. Krieg Arc ---> Someone light years way stronger than Krieg appeared & who faced him? It was Zoro & then he left the Arc. Which again shows that Oda create more Excuse for Zoro to let Luffy fight the Villain & not handle it himself
5. Arlong Arc ---> For the Fourth Time in a Row. That's Crazy! Oda again gives justification on why Zoro cannot Fight Arlong & must let Luffy do it due to Injury from Mihawk
So literally in whole East Blue Saga, Zoro was Introduced & Portrayed as the one who's Role is to Fight & Protect Luffy & face Villain first but Oda always creates an Excuse to make Zoro unable to Fight or Occupied & then Luffy takes the Stage, because obviously he is the Main Character & not because he is the Strongest
And this continued more & more:
Zoro was the one who's gonna fight Bellamy but Luffy then told him to stop & let him talk
Zoro was the one who remained at the end of Skypiea Battle Royale & faced Enel before Luffy but similar to Buggy, only Luffy is compatible with Enel
When they were riding Train to go to Ennies Lobby, Luffy ordered Zoro to handle both the CP Train & T-Bone
In Thriller Bark, it was Zoro leading the fight against Oars & when Luffy arrived, it was only thanks to Nightmare Buff & Team Work that they managed to defeat it & after Luffy handled Moriah, it was Zoro who fought Kuma & saved his Captain
It was Zoro who fought Hody first & defeated him
When a Dragon attacked them, it was Zoro who took care of it
It was Monet who prevented Luffy from capturing Caesar at first & who handled her? It was Zoro ofc
When Luffy was gonna go save Law & Pica blocked the way, it was Zoro who fought him & Luffy said "Zoro can handle anything".
And when they were thrown from castle & jumped to try & reach it again, they were attacked by Senor Pink, Machvice & Dellinger & it was Zoro who took care of them & then Fujitora stood in Luffy's way & it was Zoro who stopped him & then Pica attacked them again & it was Zoro who stopped him
When Zoro wasn't included in an Arc, do you know what happened? Luffy couldn't fight Main Villain of the Arc & had to settle with the No. 2
When Hawkins attacked them, it was Zoro who had to handle him
When they met Urashima, it was Zoro who scared him & not Luffy
When they entered Onigashima & got attacked by Apoo & others, it was Zoro who had to carry Luffy & protect him
When they reached the roof, it was Zoro who saved Luffy near a dozen time & it was him who had to face Hakai before it hits Luffy & it was him who hurt Kaido using CoC before Luffy realizes it ... etc
The Pattern is Clear:
Zoro is Strongest In Crew, his Role is to Protect Luffy by being Best Fighter but since Luffy is Main Character, Oda always make Excuses & Scenarios where Zoro is unable to finish off the Villain & Luffy has to deal with him & crush his Dream
Even in Movies, for example in Film Z when they first fought Zephyr in Kitchen, it was Zoro portrayed as the best fighter of monster trio & when they faced Gild Tesoro, it was Zoro who attacked him first & in Movie Stampede, Zoro was the one who prevented Fujitora from entering the battlefield.
Even if u go to a Special Video which is Non-Canon, you find Luffy + Law teaming up on Kizaru & Sanji fighting Sentomaru while Zoro going toe to toe with Fujitora alone
the reason is oda gave them yaol vibes they cant live without each other boner 
and let's not talk about probability there 
