If you have enough horses for your troops, and keep goods under troop count (goods, not crates, mind you) you should be able to move at about 30ish speed. (Under 30 when the troop count is high).
Which is certainly fast enough for me. If you are carrying more goods, yes, there is a speed or investment requirement. This is part of a thing called "balance."
Did you miss the part where 2000 good caravans were intentionally nerfed?