Panama is not necessarily that underdeveloped. It is a middle income country as is Colombia. Colombia due to its size and war is more uneven in the development of infrastructure. Having towns only accessible by boat is not necessarily a measure of the capacity for a country to build infrastructure. It isn't that uncommon for even a rich country to have areas accessible only by boat. Consider Jeanu, Alaska.

Northern South America has some incredible challenges when in comes to terrain in general. The former columnist on Latin America at the Economist left it as his final thesis that this fact explains why the region is not more rich, despite a wealth of natural resources:

https://www.economist.com/the-americas/2022/12/08/latin-amer...

If one has ever been on the road between Villavicencio and Bogotá or passed through Tungurahua to Pastaza in Ecuador they can appreciate the difficulties that were overcome to build those roads. The rough terrain is one reason why less than 50 miles from modern cities in Ecuador there are still uncontacted native people. Given this northern South American baseline, if someone who knows the area says the terrain is unforgiving it is unforgiving.