I just want to move my army onto dry land, but pathfinding demands that it go off into the unknown looking for a harbor that doesn't exist because this is uninhabited land. I feel like the game needs some kind of check so that this doesn't happen.

Pathfinding in general is pretty borked 

Still not fixed in the newest beta patch. I wonder where their priorities are.

It is not as bad as you think, but It is as annoying as you think. to land units the pathfinding needs to "see" the tiles around your landing spot. It is a fog of war issue that can be worked around by sometimes backpathing.  What can help is waiting to try to land at the start of the turn with full points. Also split off a unit to either side of the main stack then land the large stack.

I hope this is helpfull for the future.

That is still a work around when it should not be an issue at all. I also want to land my units, why do I need to know all tiles around the landing spot? I have not seen anything similar in other games, so to me it look like a bug that very much should be fixed given how annoying it is, especially with early game transports that can die due to high seas that they sometimes decide to travel to when you simply want them to disembark.