So, uh, why didn't they bother to include an actual story into these games? Both of these are huge 100+ hour epics, yet the plot is just as straightforward as the original Donkey Kong, and the characters and world aren't given any development whatsoever(if anything, TotK seems to have contempt for people who held on to what little story BotW had)

I'm not arguing for the games to have long ass cutscenes or dialogue dumps either - these games already have way more exposition than other games that are praised for their story and setting like Elden Ring or Ocarina of Time. You could just take the time that was already allotted to cutscenes and dialogue and, you know, do something with it. The games already have a ton of exposition, they just don't do anything with it