Social and fiscal incentives work. Indoctrination works. Propaganda works. They are almost always used for nefarious means, but ultimately, they are tools.

Beyond this, heavy-handed government-side rules can exist to drive population opinion. In example, to reduce vaping in youth, many places have banned child-advertising of the products, including things like child-friendly flavor advertisements [many states cannot advertise "liquid candy!" as a vaping product]. You could make it illegal to advertise anything "child oriented" on social media, from facebook games to Elsagate-style schlock, show no kids using Instagram, restrict TikTok ads on TV to late night timeslots and internet ads for it only on age-restricted websites (banish it to the same rules as pornography ads, basically). With no financial backing, no profit to be made in wasting large amounts of bandwidth dollars, thus the market will contract, GDP will reduce (oh well), and the consumers will consume less.

It's simple enough, really. It's just work. And will have a whole bunch of "influencers" complaining and smearing you for restricting their access to your children.