If you are a board game enthusiast, chances are you'll eventually get bored with basic rules and want something more complicated that allows for interesting game mechanism or complex decisions. If you look at Board Game Geeks top games, a lot of them have a high complexity rating.
I'd note that sometimes complexity comes from surprisingly simple rules, like with Go or Chess. Next to Terra Mystica, Go or Chess might appear simple.
If you are a board game enthusiast, chances are you'll eventually get bored with basic rules and want something more complicated that allows for interesting game mechanism or complex decisions. If you look at Board Game Geeks top games, a lot of them have a high complexity rating.