I have been active on internet forums since the mid-late 90s. Facebook and Instagram and their other social media didn't create any of those bad human traits, they were rampant to begin with.
What these normie-networks did do was make a UX for public posting so easy that scores of low-education users were able to be influenced and re-share low-infromation-quality stuff in huge magnitudes. FB is guilty of making a super accessible user experience, and then in not being aggressive early enough in having high standards for its userbase. But it didn't invent society's ills.
I found myself stepping back from social media and deleted a lot of my accounts in 2016 -- the election and the Cambridge Analytica thing was a big reason. LinkedIn could have been the worst because I had spent so much time promoting myself and prospecting, I met a lot of good folks but I also met so many bullshitters who helped make me into a bullshitter.
The influx of normies circa 2000 did not seem so bad to me but Facebook and Twitter were another thing.
What these normie-networks did do was make a UX for public posting so easy that scores of low-education users were able to be influenced and re-share low-infromation-quality stuff in huge magnitudes. FB is guilty of making a super accessible user experience, and then in not being aggressive early enough in having high standards for its userbase. But it didn't invent society's ills.