The specs are meant to be an Islander replacement - passenger load, take off and landing distance, etc. Twin Otters carry twice the passenger load, so not a 1-to-1 replacement. Cape Air also operators a few Islanders, I’m sure they told Tecnam EXACTLY what they wanted in a replacement.
DC-3s are (still) great (go Basler!), but all the new utility aircraft have things that can’t be retrofitted to that airframe. The Skycourier has so many features that will make it perfect for its application: square cross section, container-sized cargo door, high wing, fixed gear, etc. New utility planes like the Skycourier or P2012 STOL may not make many trips to Antarctica, but you only need a few Basler 67s to fill that need.