I have contemplated this although I'm not yet in a position to face it myself. But I can draw on my own experiences seeing the modern, engineered-experience internet gradually grow up day by day.

The critical thing, I think, is not to hide them from the bad and act like the entire job is done - because then at some point later, you open the door and shove them through it saying "ok, you're ready kid" and they aren't - but to expose them and prepare them in ways of "extracting more from less" - to feel self-sufficient so that they don't get stuck in a bad habit. So blocking can be used as part of the solution, but it has to come with some alternatives. What we're looking at with our information society verges on "basic life skills." The way of the algorithm is to leave you slightly unsatisfied and clicking into the next video, sharing more than you need to, begging for attention. What is the way around it? How does one train themselves to stay safe online in the same way that one learns to tie shoelaces? (I've known adults who gave up on tying their shoelaces. It is a pitiful sight.)

Well, you can visibly take up a hobby of media analysis and philosophical critique. Take the content, identify how it works, and add your critique. If it's entertainment, you can look for technical breakdowns of how it works. If it's politics, find the part of the argument that is a contradiction, because all ideologies have them. And that can be the dinner discussion. Doing that week after week for years will give them an awareness of media that they won't acknowledge as anything special, but will reveal itself abruptly when they start calling out their friends for consuming trash and getting into vicious arguments as a result. And then they can learn to not read their replies. Remember, we're looking towards "what happens after you let them out the door". One path leads them towards being employed as someone's intellectual footsoldier, regurgitating whatever memetic information is out there and living a life that is not entirely their own. Another is to give them exits and ways of being that are genuine to their inclination. Working on yourself and your issues gives them the example to follow, so always look to do "things for myself that my kids can also learn from". Like, my dad had a focus on healthy diet and exercise, my mom did not. Guess which one I followed? My dad, of course. Not immediately in every sense, because I also tried mom's ideas, but I was aware of it and grew towards it. That's what saves a person.

And so...also give them books that are disconnected from the online experience, the "good books" that nobody talks about but everyone recommends, in all subjects. There are a lot of them, and the level of content is so far beyond the average reaction Youtuber. And there are really good Youtubers too, who usually aren't doing clickbait and so aren't the most polished or popular. You can download and archive those, and that will be fine up through the grade school years. But you have to keep up with the subjects that they're interested in, and this tends to shift around really quickly until they're near adult age. And often people just can't hear things unless they like who's saying it, so some valuable advice will inevitably be overlooked. "Youth is wasted on the young" is a basic rule. So you have to not look at it in terms of bringing up their averages. If they grow up knowing "here are some good ways to live" and they still reject all of them, that's not the end of the story, and they may come around in time.