Maybe it's just me, but I'm not bothered by their focus. Nor do I think it's at the detriment of the Strawhats. I think Oda could do with giving them better things to do, is all. That's the real problem.
Yes, that's exactly the issue. For instance, Kinemon in DR does nothing of real substance except dressing like DD and rescuing a Snitch. You could have easily deleted him out of that arc and you would not notice. To make matters worse he is not really cool, handsome, likable, and his fart jokes are awful. He is more of a joke character. He possibly has the most screen time aside from Luffy in the TS and he never made to the top 100 ( he might after this arc) in the character polls. I have no idea why Oda loves his character so much. I think the only time I actually connected with him was with the whole Tsuru thing when he was being reckless, irresponsible, and stupid.
Tashigi being in DR would have been my choice. She is attractive, likable , and has a really high degree of chemistry with any of the straw hats without breaking the hierarchy of strength and status of the crew (looking at you Jinbe). DR is the equivalent of Alabasta, Tashigi actually winning a fight and succeeding in saving the royal family would have brought actual character development, and stakes instead of Fujitora doing nothing and looking confused asf. I don't know maybe Oda is saving this for another arc.
To put it simply
If you only had one spot for a supporting character in Dressrosa... Who would you pick between between Kinemon and Tashigi ?
For the Sanji rescue arc, who would bring most stakes and depth between Carrot and Robin ?
The answer to both questions is pretty obvious
