I'd like some Anno 1800 guru to explain this to me as well. Since the game's launch (i.e., nothing to do with any patch, current or past), the OP's described train utilization behavior has been present. I don't even bother upgrading the harbor depots with more trains any more since there's no point as they never get used.

I meticulously lay out my track network, too, so there are no bottlenecks and multiple paths, so that's not the problem.

So why is it that when I am setting up a trade route, if I mouse over an NPC's harbor, the game will pop up a tooltip message box showing me all the goods that NPC is offering (as well as what they are requesting), but when I click on the ship's "Load Item" button (for that harbor), it, at best, displays different items being offered, but most times shows them offering nothing at all? (And mouse over the harbor again, it still show them offering stuff, so this isn't some timing thing or that some other NPC trader just happened to come along and buy up all their goods.)

Is this a bug or a feature? I haven't played in about a year, but I don't remember this being an issue before.

P.S. Though it would be a good guess, no, this is NOT an item filtering faux pas on my part.

I'd like some Anno 1800 guru to explain this to me as well. Since the game's launch (i.e., nothing to do with any patch, current or past), the OP's described train utilization behavior has been present. I don't even bother upgrading the harbor depots with more trains any more since there's no point as they never get used.

I meticulously lay out my track network, too, so there are no bottlenecks and multiple paths, so that's not the problem.

Is there any paving that the little NPCs will actually use?

I haven't unlocked Investors yet, so the only generally available ground paving I have at my disposal is under the Artisan's "Pleasant Esplanade" tab, but the game's citizens won't walk on it.

Same applies to using paving in the Museum and Zoo structures. What's the point of paving elegant, nice looking walkways if all the NPCs just hug the border exhibit tiles and can't reach/access the benches and whatnot I place down for them?