he literally sent sanji flying with his tail. Sanji couldn't do shit to drake. He kicked him in the face and drake didn't even flinch. Yes, Vergo cracked Sanji's leg but there are two very important facts
- It was already shown that Sanji's leg was damaged from injuries he got when his body was switched.
- Characters get stronger across arcs even if they do not get a tangible power up. This is a fact and a common trope across mangas. Rayleigh even stated that Haki blooms under tough situations. Hence, Sanji's haki would have surely grown from his fight with Vergo, his fight with Doflamingo, his fight with Judge, and every clash he had with the big mom pirates in WCI. In fact you can literally see power growth from Sanji within WCI. At the tea party, Sanji was unable to block a move from Daifuku's glaive, yet while he was on the sunny, he was able to block a hit form a far larger genie that daifuku produced, and at the same time showcased CoA hardening(something that is somewhat visible in the manga but blatantly confirmed in the anime). In any case, there is no reason to believe that Sanji didn't grow even a little bit over the course of 3 arcs.
you're literally contradicting yourself. Sanji is a CoO specialist, he should have been able to detect Drake's attack. He got hit because Drake is a better fighter and is overall significantly stronger than Sanji.