Nami is tertiary side character whos only job now is fanservice
This is such a myth. Nami was heavily involved in the main themes of damn near every arc.
Fishman island = Victim of racism/ resolution with Jimbei.
Punk Hazard = Saved and freed the kidnapped, drugged, and experimented on children.
Zou = Was the most highlighted strawhat, she was narrating the Sanji flashback.
WCI = Emotional anchor throughout the entire arc, when Luffy was fighting Katakuri she was the one giving the strawhats a reminder on respecting the Captain's order. She was also pivotal in taking down a sweet commander.
I don't even know why people keep parroting this when Nami is more prominent than probably even Zoro in most arcs, or are we judging by panels dedicated to fights only? Every strawhat bar Luffy took a hit post skip Nami is no different but even among the strawhats she saw her role reduced the least.