The slippery slope argument is hugely valid, but having kids not have access to alcohol, porn and guns is very normal. We don't even discuss it in the 'physical world' because it's absolutely normative.
Even in 'Europe' kids aren't going into the liquor store stocking up obviously - there are always age and responsibility-related conventions.
The 'online' nature of this piques our anti-authoritarian triggers and tends to err our judgment a bit.
There are valid reasons to do this, and there is 'a right way' - maybe we should have some hope and promote that.
I'm not hugely optimistic that they'll get it right, but we should aspire for to build the world we want. There's enough momentum that it's plausible.
In europe drinking age is what 16? By the time you want to regularly drink you are already legally allowed to. Meanwhile in the US you get screwed by both the law and your university for drinking in a dorm at 20 years old.