There are some VC-funded companies in this area, but the vision/AI part is pretty much solved. It's getting the mechanical systems to be robust enough in a very dirty environment that's hard.
The big insight is that most of the separation has to be done by cheaper processes operating on the bulk material stream. The robotic system is just to pull out stuff that didn't get sorted correctly by screens, drums, shakers, magnets, blowers, and vision-based air jet sorters. An all-robot system is too slow and too expensive, but quality control robots for getting from 5% contamination to 0.5% contamination are cost-effective. Here's a good video of the whole process.[2] 70 tons an hour.
That makes it possible to get contamination levels down to China's new standards and the ones of US plants which can use the stuff. "Because of China's voracious appetite for all types of U.S. scrap exports over the past 20 years, MRFs "had the luxury of being able to sell the mixed rigid plastics [and] mixed paper without a lot of sorting and quality control." ... "Some materials are up in price … PET is actually increasing. It's a supply and demand thing," Butler said. "For the most part, if you can separate that material, there are domestic markets for that right now."[3]
So, in the recycling industry, some are whining about China's policies and others are fixing the problem, shipping products, and making money. It's small and medium sized cities that can't keep up. The big cities have big plants with multiple 70 ton per hour processing lines with the machinery running 2 shifts a day, and direct deals with companies that can use the plastics, metals, etc. A small town doesn't generate enough recycling to do that, and trucking unsorted material long distances is too expensive.
[1] https://resource-recycling.com/recycling/2019/05/07/how-recy...
[2] https://youtu.be/4FpsH_ETT7c
[3] https://www.wastedive.com/news/china-contamination-standard-...