Red tape is definitely an issue, but freight costs to Nepal are also extremely high. It's a landlocked country with very poor transportation networks. Air courier (eg DHL) to Kathmandu is in the range of $5/kg, and if the final destination is in a village it needs to be hand-carried there. So accessing cheap stuff from abroad is much harder than we might think coming from developed countries. There is no such thing as slapping on a FedEx label right to the final destination.

Could go the opposite way and welcome everyone and everything in, and have situations like your ports being bought by China, as is happening in African nations.

This is the problem in many emerging economies in SE Asia. Just because many people are struggling to arrange their daily meals, Governments get into socialist mode and taxes anything which does not classify as bare necessity. Sadly, it is a vicious loop and these economies are not modernizing enough at a rapid pace despite so much talent waiting for an opportunity.