[Mithalwen]

I think the elf's response to Sam showed that he could learn however whether he could get to a comparable skill level given the relatively small window of opportunity for mortals compared to elves who while they mature physically slower than mortals, gain mastery of their bodies quicker and do not deteriorate with age. Mortals absorb information easier in youth but skills improve with practice but their bodies age and may lose strength or capacity. So a mortal might just not be able to get the skill due to time. Though rope might be relatively straightforward. The other factor is materials. It maybe that hithlain, like the special corn used for lembas would only grow in Elvish lands so that they couldn't make true elvish rope only use the technology with available materials like methode champagnoise compared to true champagne. I don't know if more information is given on hithlain outside LOTR.