There is no lack of imagination here, there is realism. You think you display "imagination" by just regurgitating all the tired tropes of old science fiction? Oh wow! Robots to clean the ocean! How novel! Nobody has ever thought about this!
The reality is nobody is going to build robots to clean the ocean because there is no money to be made. There will be robots to clean rich people's pools, sure. And it will put pool boys out of a job, great.