Naruto was a complete weakling in beginning and middle of Shippuden until he actually learned sage mode. Then Naruto's power increased exponentially when he learned to control Kurama's chakra as well.
Luffy was already far more powerful than his preskip version even with basic Haki and it was a very visible gap unlike Naruto when you felt he barely made any improvement. Even Sakura looked stronger at the beginning. That's like FI Nami outperforming FI Luffy in strength and power.
Also, Hebi Sasuke easily owned Naruto, Sakura and Sai without struggle. The difference between Hebi Sasuke and Naruto was wider than the difference between Kidd and Shanks.
Also, current Luffy isn't busted? Having highest application of CoA, CoA and ACoC. On top of having an awakened god fruit which allows him to warp reality like a cartoon, you think that's weak? It's gonna be more overpowered from now on.
Don't kid yourself to believe he's weak because Kizaru tanked his attacks. That's cause Kizaru is HIM.