Even buildings that are not ignored often look dipolated in China. The apartment I was last living in was a 2010ish, considered a nice place, but you could already see some concrete crumbling and of course, Beijing is a dingy place because of the sand and dirt.
I think most residential construction in China has a shelf life of around 30 years before they have to tear it down and do it again. This is because they favor labor intensive but skills light concrete techniques that require a bit of overbuilding. That way, they can keep uneducated migrant workers employed.