You should understand the fact that toei did a lot dirty with sanji,King vs sanji fight was short in both manga and in anime but we can see that the fight was different from manga and they downplayed sanji just like the recent sanji and s shark confrontation after all that now this to.
I think if it wasn't for the plot and if oda made sanji fight pica just like Zoro heavy cut sanji kick could have caused a huge impact,and also comparatively sanji didn't even struggle that much to defeat queen if compared with Zoro if given more time sanji can give a good fight to king and even high chances of defeating him and also sanji could have gone head to head with lucci,but he was busy with Saving bonney from kizaru
