That's only true for reproducible "random" systems, like passwords. Creating something random as a human is very easy: if I draw something on a piece of paper, scan it, and hash it, there's no way anyone (including me) can ever reproduce it! Doesn't that make it random?
I could always find digital copy of your scan and reproduce your drawing easily, how do you think people created fake money, coins and paintings since the beginning of time.
If I can reproduce your painting in any way that means it's not truly random, and there is a bunch of academic papers and research that can prove why you wrong, and why you need to read more about this to understand it better.
People are bad not only bad in creating but they are also bad in detecting randomness because it's hard, and you can read more about it in this Berkeley study:
https://cocosci.princeton.edu/tom/papers/hard.pdf