It's almost an emergent property... don't think it quite qualifies as a "mistake". It was bound to happen
I'd personally rank the careless use of plastics for nearly everything conceivable including the most unnecessary stuff higher in our collective mistakes list
I think your response is extremely unimagnative. We had the internet in widespread use for a decade before 'social media' was in widespread use.
Social media of the kind being discussed here-- mass market sites driven by algorithms designed to hack human behaviour and drive "engagement" at any cost-- is may be an inevitable consequence of advertising funded business but I don't believe it is an inevitable consequence of the internet.
I'd personally rank the careless use of plastics for nearly everything conceivable including the most unnecessary stuff higher in our collective mistakes list