In Mario Golf: Super Run it's fairly simple to unlock every course, but it's impossible to play all of them while staying under par.
When you first launch Mario Golf: Super Rush, you can only enter five courses. However, by playing the game's golf adventure mode or completing 18 holes on a regular tournament course, they will be able to unlock another four holes. Technically, the game does have a 10th course, but Super Golf Stadium can only be used when playing Battle Golf mode of the game.
While some may be disappointed by the limited number of courses in Mario Golf: Super Run, it's hard to argue that they at least offer a lot of variety. Each level has its own unique challenges to overcome, and those challenges become more difficult as the player progresses.
Mario Golf: Super Rush is a game that keeps giving. The 2.0 update to the game was released in early August, adding a new character and a new class to the game, and recently released another major DLC. As with the last game, you don't have to pay a penny to download it, and you don't have to wait a long time. Even better, the Developers of Camelot seem to have doubled down this time, adding two new playable characters and two new lessons in the 3.0 update.