The thing is the strawhats will eventually be on a different level than most supernovas. It might even happen at the end of Wano. But right now, they are on the same level in the sense that they cant low/mid-diff one another.
The biggest argument against it is Luffy himself because he defeated Doflamingo, then Cracker, and then Katakuri. He also has a 1.5 billion bounty and falsely called as the fifth yonko. Can other supernovas beat Katakuri? Probably they cant, but they will give Kuri way more trouble than people believe. Uruge already defeated a sweet commander. Kidd injured a sweet commander and stole something. So they are not scrub to Katakuri.
Luffy is probably the strongest of the group. However, the moment he faced Kaido, he got one shotted. I still remember people were ridiculing Kidd and his alliance because they got destroyed by Kaido. The result was exactly the same when Luffy faced Kaido, which means their distance from the WSC is nearly the same. In fact, Kidd and Killer probably did better than Luffy as they didnt get one shotted.
In Udon prison, its kind of obvious what Oda was doing with Kidd. Him having CoC, getting panels side by side "I will get you Kaido", carrying equal amount of rocks, healing at an abnormal pace like Luffy; stuffing, and shrinking also at an abnormal pace like Luffy all hints him being close to Luffy in terms of strength.
This is a long anticipated arc where most supernovas gathered at the same place. The last time something similar happened was at Sabaody. I highly doubt Oda will show at their first meeting how Luffy or Zoro is so far ahead than other supernovas of worst generation.