It's hard to think of a single place where planning has created an amazing city. Maybe, Vancouver, maybe, but that's mostly a success because it enables a small number of towers in the downtown core.
Despite the huge amount of construction over the past century, the best parts were made when there was the least of contemporary planning methods.
I think a lot of it comes down to the planning for required cars. But the entire field is a complete failure, once you look into how it practices itself in the US.
And if you talk to planners and call them out of the failure of the field as a whole, and for the particular projects they are in, they will say "it's not up to us it's up to the politicians." Which is rather revealing. "Planning" isn't planning but instead a thin veneer over politicians following the whims of NIMBYs.
We'd be better off without the entire field. Let's start from scratch.
We need building. We've done enough planning for 10 lifetimes, and all it got us was a crushing housing crisis.