By and large, I'd expect people using mixed-case table names to get accustomed pretty quickly to the fact that they have to double-quote those names in SQL. I don't see why it's a surprise that that is also true in \d commands.
Every day the number of people increases who get mixed-case names in their DB because their client language preserves case and doesn’t require quoting.
And it isn’t like any sane person is using case to distinguish names in their DB and so would be at risk of seeing multiple unwanted matches for any given pattern.
I don’t think name pattern matching during object lookup is a good tool to wield to try and convince people that using camel case is a bad idea and they should use snake case instead. If they don’t write enough raw SQL to be annoyed by their choice more power to them, making \d more accessible for them is a win and snake case people won’t notice or care.