In an announcement on its website, Nintendo confirmed that the YouTube app for the 3DS will be officially shutting down on the 3rd of September. They note that the YouTube app will continue to exist for both the Nintendo Switch and the Wii U, although we can’t imagine that support for the Wii U will continue much longer either given the focus on the Switch these days.
It is a bit of a pity that the app will soon no longer be available and it is unclear why the company is doing that. For the longest time, it has been speculated that the Switch could potentially be used to replace the 3DS. In fact, just recently, Nintendo launched the Switch Lite which is a cheaper and even more portable version of the Switch, making it an ideal candidate to replace the 3DS.
However, Nintendo did previously deny that they would be replacing the 3DS, stating that they will continue to support it as long as there is demand for it.