Yea and that makes sense to hold that opinion or perspective of things. But I would say it's not necessarily true, a lot of games focus around building new loot drops, new class skills and talent trees, and new quests and encounters, and world building, and every once in a while they introduce new gameplay mechanics. Which is a change to the client and server.
SoT has skips out the stuff on loot drops and skill trees, but they do have new environment building, new quests and encounters/monster types, but more importantly they are often iterating on the gameplay mechanics. And that part I think is tricky which may take more time to figure out and test. But they've had a lot of changes to the client and server over what players can do in the game, and it's quite analog about how they do things compared to how these things are typically handled in other games.
But yes, I understand how someone would think SoT is a fairly low effort job compared to others, but in my experience this isn't the case. Sometimes it can be incredibly easier to make a lot of straight forward quest content (repetitive kill and pick up/find quests) than it is to constantly add new gameplay mechanics, in which you have to figure out all the things that can go wrong, and how to support all the graphics, animations and effects, and gameplay code that are needed for those new mechanics to work and feel good!