Simian Spirit Guide for example, enabled many degenerate combos to achieve their goals a turn faster and allowed players to cast a turn two Blood Moon or a turn one Chalice of the Void before being banned from Modern
Food by itself isnt a great mechanic but remember that it counts as an Artifact, giving Oko surprising synergy
Its unfair as it is problematic while encouraging tedious play patterns for those involved
So, even though it's not destroying anything, you can actually prevent not only the Ba Sing Se that is already on the battlefield from making any relentless 2/2 attackers, but all future copies of Ba Sing Se
As such, I just kill an opposing Thief of Sanity and move on with my life, and it has rarely done anything bad when I play against it
Mindslaver is already on many players naughty lists