Knowing Paris as it is now and comparing to the photographs in the article I am happy that cleanup was performed. The old architecture was maybe interesting to some extent, but very close to a huge slum.
There's an architectural movement to come back to these more human-sized city designs too: smaller streets, more mixed use, less emphasis on large (and motorised) transportations, incorporation of structural shading and breeze-shaping, ...
From the perspective of today the problem was that the families living in the small apartments was way too big and did not pay enough rent to maintain the buildings. They just did not have enough rich single professionals willing to pay chic apartments and studios back then. Or student with rich parents seeking a studio downtown.