Opposite - for years before any state had legalized, kids have been reporting that they could get pot almost as easily as beer or cigarettes, although the latter are much more popular among adults. Marijuana criminalization has not helped kids.
Yeah, I smoked and drank as a teenager. There was only one store in my whole neighborhood that would risk selling me cigarettes, and none that would sell me liquor. I’d either have to “peg” outside the store for someone else to buy beer for me, or I could hop on the bus and travel a couple miles to one of the liquor stores in a different neighborhood that would sell to teens.
Weed, on the other hand, I could buy from at least 3 different people at high school on any given day, and a few more people after school that we knew from the neighborhood or who would even come deliver. They never worried about ID. There was only one dealer who would actually insist on not selling to kids under 18, but the kids in the neighborhood (including her own sons) would just get one of the older stoners to buy it for them.