The reason is so annoying is the lack of variety and originality behind the Warriors storygames. They tend to not have the best grammar and spelling. They also tend to be light on actual content. They also tend to lack new creations besides new characters that help differ it from the original series. They seem to use the original clans and original settings. Maybe I'm expecting too much from children, but I created whole worlds in my imagination inspired, but not exactly alike those things that inspired them (Lion King, Pokemon, various short stories that I can only remember the details of vaguely) I was a lonely, easily bored, only child, whose mother did not allow other kids over or vice versa a lot, so maybe that is the difference.
However, I think if they were better written and more creative works, it wouldn't be as bad. Any fan fiction type works that rely extremely deeply on the original works they are derived of and lack creativity to differ from the original works are usually not see as good except by super fans of the original work. If someone wants even people not familar with the work to appreciate a work of fan fiction, it has to be well done and creative enough for them.