Open and Detailed Hub World Like Super Mario Sunshine
One gameplay aspect that Sunshine expanded on after Super Mario 64 was having a fully realized hub world called Isle Delfino. It was bright, colorful, and filled with NPCs that could give the player hints and other items. Collectibles and secrets were also scattered around the area, and exploring every nook and cranny of the island was engaging enough to make the setting of the game feel alive. It also gave the player some choice when tackling objectives; if you were stuck on a particular level, you had at least two other levels you could pop into to take a break. Given the increased power of the Switch, the new Super Mario could adopt a similar approach, eschewing the level-by-level approach of 3D World and 3D Land, and really creating a massive playground for the player to explore and find Stars in, before even hitting the first level.