Is it? What cleaned up my country's rivers of plastic after many failed projects was a government program of paying for returned plastic bottles. In poor countries (and that's where the most of plastic comes from) you don't really need complex or super-smart automatic systems to do this job as manual work is cheap. Just pay enough for recycled plastic so that it makes a viable source of profit for those in need, and you'll have a massive army of people collecting waste much more diligent than any net or automated system.