Considering the state of the world as a whole, I'd say it's better to teach kids to question authority even if in this case the law is correct. As for enforcement, even if the majority of kids still access the sites, it's better that the access is deemed illegal to keep some of the kids away. Plus it'll keep sites from being able to specifically advertise to kids, which might help as well. It's not a solution in and of itself, but it's a good first step.

past laws barring/gating access like these have shown that the vast majority of people won’t try to get around them -- and that’s actually the point. In a liberal democracy, it’s useful to have only a tiny fraction of the population understand how things really work. that small group can then be easily dismissed as extremists, just like any other fringe group. this helps reinforce the country’s mainstream narratives and propaganda since the "silent majority" seem to be going along with it.

There isn't even a plan for how this is applied, France just makes laws and doesn't go through enforcing them

Then, finally, ban it for 15 year olds as well.

Incredible. We're in an age beyond parody.