Does the “use magic device” feature of the thief subclass allow you to attune to items requiring you to be a spellcaster?
##Yes, it allows Thief rogues to attune to such magic items
Yes, it allows Thief rogues to attune to such magic items
Being a spellcaster is defined in the rules by the creature having the spellcasting feature, gained either as a class feature (e.g. Sorcerer PHB p. 101: spellcasting) or as a racial trait (e.g. Spirit Naga MM p. 234: spellcasting or Drow Elite Warrior MM p. 128: innate spellcasting). Either way the Use Magic Device feature means a 13th+ level Thief ignores this requirement. As stated in the Use Magic Device feature:
Use Magic Device (PHB p. 97) says:
You ignore all class, race and level requirements on the use of magic items.