There are many other things to do other than fighting having a 1vs1, Sanji can get good feats that aren't necessarily tied to a 1vs1 battle.
I have a hard time seeing current Sanji struggling against a Vice Admiral, unless he faces 2 of them. I might be extremely wrong but i just don't think any of the Vice Admirals are that much impressive to put enough pressure on Sanji who was simply bullying a Seraphim by himself, unless Oda proves me some of these VAs are really build different.
The 5 Chins guy is the most impressive for now because he defeated a Sea Beast Weapon it seems, but he screams "Franky opponent" to me, that "Steam Knuckle" thing sold it for me. I wonder what Kadar's grandson and Goatbeard are going to do tho, they weren't even shown fighting till know so i guess we can expect more of them... I still have faith on VAs, Vergo was an impressive combatant given the standards back then, who was unfortunately used for the sake of hyping Law's Devil Fruit at the end of PH, (before it got nerfed again lol)
And there is Saturn, who is the Godhead of Science and Defense, and Sanji is the Warrior of Science according to Oda... Bonney is Kuma's daughter, Sanji declared to Kuma he would somehow be the most feared by the Marines back in TB, and she is coincidently putting respect on Sanji's name as we saw on chapter 1090... Whatever that is going to mean, we need to wait and see...