Uh, I need to care about it because it's an important factor in planning which city should be developed as a trade hub and whether should I focus on land trade, or invest in seafaring merchants. I'm stuck in a nasty corner of an oval landmass with ice blocking my access to profitable markets. My only open marine trade routes would need to end in Venice and I despise Donadolo, the Butcher of Profitable Friendships.
If I remember correctly from pre-release conversations, caravans should have range of 10 hexes and cargo ship of 25, but even though it seems right for caravans, cargo ships cannot reach coastal cities within this range.
Could you give me more details concerning the list of modifiers you laid out? My standard difficulty level is immortal, but here I'm struggling on king...