Stubborn dark marks from old breakouts that just will not fade

I have a scattering of brownish marks along my cheeks and jaw left behind by breakouts from the last year or two. They are flat, not scars exactly, just pigment that is overstaying its welcome. I have started being religious about sunscreen because I read that sun undoes any progress on pigment, and I have azelaic acid in my cabinet that I use a few nights a week. My question is really about patience versus strategy. Is this just a matter of consistency and months of waiting, or is there something else worth adding, like niacinamide during the day or a gentle acid? I do not want to pile on so many actives that I irritate my skin and cause more marks, which feels like the trap here. What actually worked for the people who cleared this kind of post-breakout pigment?