Nintendo Announces Game Builder Garage, a Quirky Programming Game for Switch

Nintendo's brand is incompatible with an unmoderated marketplace of user created content. And it doesn't get any harder to automatically moderate games: what if a hate message is only visible when the game is in a certain state? In comparison, text, images, and sound are trivial to moderate.

Note that the various app stores partially manage this problem by putting a comparatively huge barrier to entry to publishing (it takes days to release an app and it's tied to a credit card).