I am bad at remembering names. Remembering a set of pronouns is at least as hard as remembering a name. Pronouns help when I can’t remember names. Having to remember custom pronouns defeats the purpose of pronouns.

All that being said, I’ve never met someone IRL who hasn’t picked one of the three most common pronouns sets (he, her, or they), so I see this as largely hypothetical. The internet does tend to be a space for people to test their more extreme beliefs.