Farming Settler League Uniques becomes harder as u Progress.

Hello,
i play ssf and i realized its mutch easyer to farm setter uniques from ships early as u complte port quotas in a much higher frequence than when u maxed your harbour.
This feels kinda counterintuitive because u should be rewarded for upgrading your harbour.
Im stuck in a position now that i realy wanna farm the new belt in ssf but i upgraded all my city to max already so it will take me MUCH longer to eventually get it compared to a player that has like port lvl 4 and is in white maps.
It should not be like this.