I absolutely love the idea of buildings lush with vegetation, as if in some post-apocalyptical world where nature has reclaimed the cities.
It may not be very possible/feasible, it may even be a public safety hazard, but I'm so fed up with steel, concrete and glass.
"Don't just draw them on the skyscraper, make it work." would be a better sentiment. If wind is a problem, find a way to break the wind. If roots are a problem, find a way to stop the roots, or trim the roots, and build that into the design.
But there's a pile of evidence for the benefits of adding greenery to cities, so please just don't say to stop trying.
We are natural.
Also, if we're to pick a definition of "natural" that means something more specific than "exists", cities seem like a good candidate for the "unnatural" end of the spectrum.