Things that will sell their console and games to the general public, and generally catching up with the times rather than living in the past, rather than keeping them as this niche, underdog console manufacturer they were for the Wii U, and Gamecube eras, compared to their competitors.
Nintendo needs to focus on getting caught up with the times with a more technologically impressive console, unified account system, much better online infrastructure, and games that will actually make use of all of the above. They could also stand to become less tone-deaf with the games they put out (i.e. when we say we want a new Paper Mario RPG, we mean a proper new RPG, and not a sequel to the "action-adventure" that is Sticker Star).
Not "oh hey we'll charge you to play our 10 year old games that you can already play for free, AND with enhancements, on your PC, Laptop, with VR, and even on an Android phone".
It's fine if they can do Gamecube games, but don't expect it, because it really is not (and should not) be a priority for them.