The strength between Luffy, Zoro, Sanji has always fluctuated. The case has always been Luffy >= Zoro >> Sanji.
Luffy and Zoro in combat have always been on a different level compared to the rest of the crew. For important meaningful titles Sanji has been grouped outside Luffy and Zoro. (Supernova, First Bounties, Rooftop, fight Pairs, rivals? (Smoker/Tashigi, Coby/Helmeppo, Lucci/Kaku, Croc/Mr1)...
Sanji is only relevant to the Monster Trio which only happens canonically every 400 chapters to remind us that Sanji is not weak bc he is grouped with Zoro who is very strong...
This new Wings stuff is to show us Monster Trio will not be dethroned with the addition of new crewmembers.
And like clockwork, the last time monster trio stuff was utilized was Fishman Island, roughly 400 chapters prior to this timed Monster Trio name drop (in the form of Wings). Sanji fans love this bc, association with Zoro makes Sanji look very strong without actually needing to have any feats. This way Oda can scale up Sanji in theory whilst disrespecting, abusing, and ridiculing his character 100x ways.