Very nice write-up.
Like you said, zoro's lack of fight experience against top-tier (which is something Oda intentionally wanted to do) is really the only thing that is stopping zoro from entering the admiral level. Oda did zoro dirty by not giving him quality opponents of his level since TS, and on the other hand, have him low-diff every opponent he faces (pica, monet, killer, etc).
Zoro getting Pica and Monet as easy opponents were sort of understandable if you see it from Luffy as the main character's perspective since their boss' fight showed the extent of Luffy's ability and that Zoro's near-effortless victories against them signify a changing dynamic.
Where Oda really blundered in terms of Zoro's opponents, imo, is by not bringing Zoro (alongside Usopp, Robin, and Franky) to WCI. After all, not only they did nothing of note in Wano when WCI was happening, this decision also ruined precious panel time between the SHs.
Getting back on topic, if Zoro had been in WCI, we could have had more powerscaling feats to establish where Zoro really is. Zoro could have easily handled Snack when Luffy and Nami were battling Cracker. He also could have mid-diffed Smoothie when Luffy was dealing with Katakuri. This way, none of the main fighters of BMP became throwaways and clear hierarchy of SH powerscaling was further established.
Oda's intention to hide zoro's strength became problematic especially for power-scaling. I would even say that prior to rooftop, many sanji fans were still trying to make the case that Sanji is very close in strength with zoro. This of course, has been easily debunked since rooftop.
Sadly, the notion that Sanji and Zoro are equal in power is still prevalent among many people even after Roof Piece. Mind boggling, yes, but you have seen plenty of them around here, unfortunately.
Heck, we can even argue that Oda is still trying to hide zoro's strength at rooftop by letting him eat the combined attak hakai and became near-death. This is why I feel that Zoro vs. King is still necessary, despite zoro's brilliance at rooftop.
Oh, I don't disagree about a proper 1 vs 1 for Zoro being necessary. The reaction to him winning against King with his current condition is going to be fun to watch. :cheers: