Perhaps if there was a penalty rate imposed on buildings left to rot in the hope of getting a demolition permit things might look a little different. There should be time limit on leaving buildings derilict with the council stepping in to keep the buildings viable with a charge on the owners equity in the building.
On the otherhand the experiments that have failed was it the housing or the housed that were the problem. I don't reall any Cornish fishing villages with "criminal rat runs" going through them a few smugglers coves, yes, but most are very desirable places to live.
Same with tower blocks how come they turned into such a heap of crud in such a short time- in terms of property life span, when in other countries around the world they are accepted as inner city housing. If those tower blocks were privatised dwellings would they still be habitable or even proved to be a good investment?