Its easy to list the things that the next Zelda needs to fix:
-Better story.Much better story.
-Better soundtrack(because BOTW, while still good, is one of the worst in Zelda history)
-More dungeons that are also more varied.And to shoehorn into this topic, better bosses with diferent designs
-And a nitpick of mine, make the side quest rewards better.They were terribly lame in BOTW.
My (locked) thread about how difficulty should be a decision for the developers, not the gamers.
https://gamrconnect.vgchartz.com/thread.php?id=241866&page=1