I think a large factor in why the majority of fans tend to dislike “traveling books” is how the journey affects characters, or more accurately, how the journey doesn’t affect the characters. Usually (in Western media) journeys alter those who go on them. They may come back home in the end, but they’ve changed physically and/or psychologically, and it impacts the rest of their life. However, in Warrior Cats, journeys are treated as a “monster of the week” deal where they travel somewhere else to do a side quest and then arrive back to the Clans without changing. Instead of gaining a new mentality, their personality stagnates until the journey is over. Sure, they might lose someone, but they’ll return to a status quo soon enough. Once more, traveling books are almost guaranteed to not affect the arc in a major way. Unless the Clans are moving or a group joins the lake, you can flat-out erase them from existence and not lose anything. For example, the mountains are too far away to care about. Even in the “group joins the lake” point, Warrior Cats makes them retroactively relevant to the plot by including them in multiple novels; they’re rarely, if ever, introduced as genuinely important in their first appearance. The characters don’t develop and where they go doesn’t affect the story. This is why most traveling books fail.
