How one handles their online presence is directly influenced by their IRL influencers.  Parents are one influence, as are educators/mentors, but "they're old and don't understand" (like the Will Smith song).  They're immediate peers will have the biggest influence and provide the most temptation.  Hopefully your child has a good group of peer influencers, akin to not smoking, drinking, stealing, skipping, etc.  if they trash talk in real life, they're likely doing a lot more online. 
I've found that frank talk with my kids from an early age about algos and dopamine hits, real accomplishments with lasting benefits and critical analysis of situations as they are presented vs desired (ugh, that sounds so clinical but it really isn't except in a post like this), works well.  But that's me.  Sadly, most adults didn't even possess those skills (see all the attention seekers on Tiktok fake crying over the election for clicks).
We also go over their feeds with them... To see who the algo thinks they are.  We share ours with them as well.  It's shockingky accurate to what we share with the app/algo (currently I'm a coffee maniac along with all the rest of my history, wife is really into dogs, son is into weightlifting with horror stories about steroids, and daughter is into nursing tutorials and makeup).  
Media (as with all things), in all forms, cannot be banned.  It can only be made more difficult to access and thus desirable as forbidden fruit.