Zoro being a top tier (whatever that means) since ten years ago and after coming back from the timeskip goes against any attractive narrative. That's not how Oda works, he himself stated that it's not a good idea to make a protagonist too strong as it'd negatively affect the story (and wouldn't surprise me that things like Jinbe not joining until Wano was so he wouldn't mess up the power progression of the crew); so we don't even need to counter this notion with the fact that he's struggling with a 1.3b commander as his main versus (which is his consistent ballpark when things get serious).
Seriously, in no way Zoro was a top tier ten years ago (granted impossible, any proper writer will understand why), and probably neither he's as of now.