"Link building isn't natural." Yeah, nature hasn't built any search engines. The whole fucking thing is unnatural. Links don't just magically appear because we breathe deeply and trust in the cosmos. Someone always makes them.
Yes, that was ranty. I'm going to eat lunch now.
Seriously, I get the intent but I hate the line in the sand, as if it's nearly that simple. If you write a book, you don't just lay it in a field and hope people read it -- you tell them you wrote a book. Same with content.
It's not unnatural for me to say "Hey, I've got a great piece of content that's relevant to your audience." That's not in the same bucket as buying a link on Fiverr.