I’ve always interpreted statements like “there’s no such thing as an original idea” or “everything’s a remix” not literally, but rather as a reminder that new ideas are born from a cultural context and the ideas in it, using those ideas like a language of creative expression.
I often take it a step further and use it as a reminder that new ideas are rarely born from one person but rather the contributions of many, each too small to be noticed as an “original idea”, but when viewed collectively, can be revolutionary.