Do any of the current categories include bowser's fury in any capacity? I was surprised it wasn't included as part of the sandbox games category.

The sandbox category got added a few years before bowser's fury released.

Bowsers Fury doesn't count towards the Mainline Series and unless a category really makes more sense with a non-mainline game (NSLU in NSMB Series) it's not gonna be part of any on here.