Besides the correct sibling comment that you are mixing metaphors (paperclip maximizer doesn't require nanotechnology or vice versa), gray goo is and always was

Besides the correct sibling comment that you are mixing metaphors (paperclip maximizer doesn't require nanotechnology or vice versa), gray goo is and always was an implausible boogieman. Mechanosynthesis processes operate under ultra high vacuum and cryogenic temperatures in industrial clean-room conditions, and bio-like “self-replication” is both inefficient and unnecessary to achieve the horizontal scale out that industrial part closure gets you. Such replicating nanobots, if they could even be made, would gum up really easily in dirty environments, and have a hard time competing against bacteria in any case (which are already your mythical gray goo).