I do understand your point, I just don't think it's that bad per se. If Luffy stays at gear 5 for the rest of the series but Zoro gets another 1 or 2 powerups that could potentially bridge the gap. Though honestly I would put Roger and Ray around how Luffy is to Zoro.
Luffy>>>>Zoro>>>>>Sanji>>Rest of the crew in various spaces
Roger>>>>Ray>>>>>etc
I think it's fine for a captain to be much stronger, though you make a good point about it not really being that fair to Zoro since it's his only role
It's fine for the captain to be much stronger in normal cases, but like I said the partner type RHM, at least based on precedence, tend to be much closer to their captain. And here within SHs especially, given the "role based" function of the crew members.
I don't think Roger >>>> Rayleigh is true. Look at Rayleigh's portrayal in the series. His prime is implied to be above an admiral and Yonko, mentioned by Garp as a legend in the same line as WB, consistently gets a stronger reaction from characters compared to standard top tiers. Roger will at bare minimum need a high diff against Rayleigh, it likely may go to even extreme diff.
This isn't anywhere like how Luffy/Zoro appears. Rayleigh looks like a character that can stand side by side with Roger, in authority and power. While Zoro at the moment looks like trash compared to Luffy.
Look at prime Whitebeard and prime Oden. Kaido puts Oden in his "top 5", with 3 legendary figures and a Yonko (Oda's self insert). If we are to assume these are the top 5 amongst characters Kaido faced (which is the reasonable interpretation IMO), that puts him above BM (a Yonko) that Kaido faced just a few weeks ago.
Again, a partner type RHM who can at least give a high diff to his captain.
The thing is, Oda used to respect this Luffy/Zoro dynamics in the past. Luffy wasn't always "much stronger" than Zoro throughout the series. This is why Whiskey peak was a thing, why characters confusing Zoro as the captain used to be a recurring thing, why nothing happened was a thing. Because that is simply how the character of Zoro was introduced at the very beginning, in presence and demeanor.
Even in rooftop, this dynamics was played to an extend, but largely this is barely a thing post Dressrosa.
He had a role to fill in the past. But currently, I don't know if he has a role anymore, clearly he isn't powerful enough to fulfill the role he used to fill in the past.
You are correct but that is on Oda. He stopped caring about members of the crew not named Luffy a long time ago. Zoro and Sanji's opponents are low diff and lol diff material for Luffy and don't pose a threat to him at all. The rest of the crew don't get to do anything 95% of the time. The Shs exist currently so we can get a panel of each talking about how great Luffy is and how he's going to become PK.
Probably just this yeah. Post TS, especially post Dressrosa is just non stop Luffy wank.