I don't really get why Jabra being competitive and using underhanded tactics that were admittedly not very clever, somehow devalues his effectiveness as an opponent. He can utilise tekkai while moving and developed his own fighting style using rokushiki. He has a carnivorous zoan that he uses to enhance his rokushiki techniques like shigan. What's the issue? He had a gag one time, the rest is just him being competitive.
Kuroobi wasn't goofy in anyway as well. Much more serious than Hatchi and he called into question Sanji's chivalry and his capacity to back it up. Also a serious challenge underwater and was also very strong at the time, Sanji was just much stronger.
Ultimately, if you want sanji's opponents to be like someone else's, you're not in luck. Sanji's opponents contrast with the other strong members of the enemy organisation in the arcs they appear so it'd be kinda repetitive to have all of them be constantly serious or brooding or whatever so sometimes they have their gags. Different ain't bad in my opinion.