TOS didn't really do character arcs like SNW. Character growth was often confined to the episode. (and sometimes forgottenSci-fi/adventure plots are key too, though. The Doomsday Machine is the story of Matt Decker (whose story is tied entirely to the episode rather than part of a wider arc) but it's also just an exciting thriller story in which Kirk kamikazes a big space turd. Stories like A Taste of Armageddon are overwhelmingly just about imagining a fictional society rather than giving the recurring characters any discernable arc or growth.

Thinly-drawn device describes how most of Trek engages with science and science fiction. It's rarely about the science. The science is the vessel to serve the idea or the conflict on. As Gene says in my sigthink part of peoples' complaints arise from the way in which SNW engages with science fiction - it's often either a thinly-drawn device to enable some relatively mundane character beat (eg the aliens who force Chapel to say she loves Spock in S2), or is treated entirely as a joke to enable a gimmick episode. Both approaches are fine in isolation and common throughout Star Trek, but you can see why they start to wear on people when they come to define the entire show, especially with 10-episode seasons.
"Tell your story about people, not about science and gadgetry."
One of his other rules is "Don't try to tell a story about whole civilizations .We've never yet been able to get a usable story from a writer who began... "I see the strange civilization which"