If it's been used as an adjective since 1846, I don't know why it's shunned.
However, you should feel free to avoid its use as an adjective if you wish. I will continue to embrace it as both an adjective and noun.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.