Yes, Law is on panel so by that logic he is involved in the story. That doesn’t mean Law is making any straw hats less vital to their captain so he’s not “intervening on straw hat moments.” Straw hat moments are just that.
If you’re saying you want Oda to spend more time developing the Straw Hats only, I think that is unrealistic because the story is encompassing the entire world, Oda can’t just focus on 10 people forever. He got to develop and utilize other characters as well. If anything Law helps the story. I think Law helps Robin’s plot for example, by actively giving her someone who is a D. And connected to learning about history, unlike Luffy.
Also, Sanji was never a tactician, he was a spy guy and still is, his character is after James Bond. Bond was not a tactician. He was a resourceful and intelligent field agent, just like Sanji, who comes up with things on the fly to help the straw hat crew. Law is a chess master, calculated, planner type. Not like Sanji at all.