The phrase "abyss of irrelevant idiocy" is a harsh criticism that can be used to describe situations, ideas or people that are considered to be completely nonsensical or worthless. However, there are many other terms and expressions that can be used to convey a similar sentiment. Some examples include "a complete waste of time," "utterly pointless," "absurdly irrelevant," "completely meaningless," "total nonsense," and "devoid of any value." These alternatives allow you to express your frustration or disappointment in a more nuanced and less confrontational way, while still conveying your true feelings about the situation at hand.