Baia Domizia is only a little place within Campania. A purpose built village - right on the beach and it's mainly 'open' only during the Summer months. There is no rubbish piling up there simply because there are hardly any people in the place at this time of year. It's a holiday complex used as a weekend and summer place by Neapolitans.
The centre and historic areas of Naples are also for the main part clear of rubbish, but the surrounding areas like Pianura and Casoria are buried under the rotting bags of rubbish 3 metres high. It's not right to understimate the size of this problem, but as Esther75 says, it has been going on for many, many years. (I'm 47 now and always remember this spazzatura problem flaring up every couple of years or so).
This was filmed 6 days ago.