Apart from the tone of your message, I agree only partially on the content.
I agree that the technology is not the solution.
But supervision, as you say, is also not a complete solution.
In my experience (father of a now adult daughter), the best was to explain, discuss and educate my daughter. When my daughter was around 6/7 years old, I slowly showed her to lookup stuff on the internet, where there are interesting things and als explained her about "dangerous" and "inappropriate" content there could be.
But what was mot important was trust - i.e. I explained her that I trust her fully not to misuse the freedom I was giving her, when, at around age of 8, I allowed her to access the internet on her own. I explained her, later, about the dangers of posting inappropriate content on the internet e.g. on Facebook, or other social networks and what consequences it might have for her now or in the future.
But I always made clear that the decision would be hers, that I would always be there for her if she found something discomforting or felt that she did something discomforting and that I would help her as much as I can. I made clear, though, that there certain things where even I can't help (full disclaimer, I have strong IT/Software/Internet background) - and that the best would be that should be careful.
When she started using Social Networks, she then friended me (not me her) asking whether I could let her know if she posts something that could have negative effect on her or her future.
This was the same approach with my nephew (he is 16 now) about 4 years ago and this is the same approach with my god-son: trust, education, and help - less so "control" or "supervision" - and the funny thing in the end was that all three of them asked for some supervision when they started using social networks, etc.
Lastly: I showed all of them where they can find really interesting content that could be fun as well as where they can learn things - but this required to first understand what they really liked and were interested in (Daughter: Science, Knitting; Nephew: Singing, Police-Work; God-Son: Minecraft, Minecraft-Mods, Software-development, Games-Dev).
Hope this helps from a father, uncle, godfather