According to an official announcement by publisher Nintendo, the original Wii U version of Super Mario Maker will be removed from the eShop on January 12, 2021. At this time, online support features for the game will be discontinued. This means that players will no longer be able to upload custom levels which they have created.
However, Nintendo has confirmed that it will still be possible to download and play levels which were uploaded prior to January 12. In addition, players who previously purchased the game via the eShop will be able to re-download it if necessary, even following its removal.
In addition, Nintendo will be shutting down Super Mario Maker Bookmark, a website which allowed users to search for uploaded levels, as well as rank their favorites and bookmark ones they enjoyed for later play.
None of these changes will affect the Nintendo 3DS version of the original Super Mario Maker, which does not support the uploading of user-created levels.
Super Mario Maker was the first in the series of building games, which allowed players to create their own levels and courses inspired by titles from throughout the Mario series. It was followed up by Super Mario Maker 2 on the Nintendo Switch.
Presumably, Nintendo is making this change in order to focus more closely on online support for Super Mario Maker 2, which released June 28, 2019. Courses can still be created and uploaded, and the game can still be purchased for the Switch. Super Mario Maker 2 includes a number of new features, including a story mode which features over 100 Nintendo-created courses, as well as both local and online multiplayer including a cooperative course creation option.
Fans of the Super Mario Maker series are encouraged to upload all levels and courses they wish to prior to the deadline provided by Nintendo. Those who wish to experience continued online support are also encouraged to try out Super Mario Maker 2.