The issue is energy. Energy to build the robots, energy to power their efforts. Both the power and the plastics come from the same finite fossil fuel resources

The issue is energy. Energy to build the robots, energy to power their efforts. Both the power and the plastics come from the same finite fossil fuel resources and will get ever more expensive as extracting that resource gets more expensive. To tackle the recycling problem we have to tackle the energy problem or we'll make no progress addressing the essential cost. The only viable thing to do otherwise is reduce plastic production and use.