Magic items that require activation are things like Wands and staves. That blurb is basically specifically so a fasthands Rogue can't dip one level into Wizard and now can bonus action use a wand of fireballs and sneak attack. Or bonus action use a prismatic spray from one of those Brilliant Helm diamonds and then sneak attack someone.
You can use potions. Drinking a potion is using an object, not activating a special command word or whatever. Same with poison.