Actually, more I think about it, I wouldn't be surprised if Shanks/Dracule/Dragon/Saka/Teach have already surpassed that level.
Not a mere coincidence that Oda had Shanks leave Elbaf before bringing in Imu. And not a mere coincidence that he gave Shanks that joyboy comp before this arc started. Even throughout the flashback, Shanks at a very young age was still slicing and dicing an amped Harald.
I think people simply overrated how strong Luffy had become in Wano, which I had been consistently saying he wasn't a solid top tier yet. And thus by conjunction overrating everything happening since then, including this fight. His performance against Borsalino is a better assessment of where he stands in powerlevel coming into this arc, which is def not a legit top tier.