What a load of hand-waving. "Planned cities always fail?" You mean like Chicago? https://en.wikipedia.org/wiki/Burnham_Plan_of_Chicago
What I mean is to compare Manhattan, which was loosely planned, with Levittown (https://en.wikipedia.org/wiki/Levittown), rigidly planned, which was the original planned city and the grandfather of overly aggressive city planning. Later this evolved into the dystopian monstrosities envisioned by urban megalomaniacs like Le Corbusier such as Ville Radieuse (https://en.wikipedia.org/wiki/Ville_Radieuse) which would have been so utterly unliveable.
He honestly should have stuck to architecting open-air prisons and slaughterhouses.
Even Manhattan got bludgeoned by overly aggressive planning in the 1950s and 1960s when tyrants like Robert Moses were involved.
Creating great urban spaces takes a lot of patience, care, and most of all, a willingness to let the city grow as it wants to, not as you intend it to.
I probably come from a much different land (India), where chaos and organic growth is the norm for cities 4000-5000 years old. However, my favorite city is Chandigarh, a city planned by the "meglaniac" le corbusier. It is a serene small town very uncharacteristic of India, with clean well planned roads, greenery, law and order abiding population (you don't know Indian drivers, but they follow laws in Chandigarh). I pin all this down to the planned nature of Chandigarh which allows city planners to control and mould how the city should look and be.
I'm not perfectly clear why you'd prefer an unplanned chaos over planned orderly city. In contrast to Chandigarh, the city I originate from is a centuries old city which has grown "naturally", and doesn't even have sewage (and Indus valley civilization had them 5000 years ago).
Not that there is a lack of "soul" or "culture" in Chandigarh, the planned aspect covers making sure the traffic doesnt crawl, there is enough greenery, and utilities and amenities are provided to the population.