>Point is, I feel like there has always been kid of a lack of a between "Kids stuff" and "Teens stuff" in media, and that "tween" over time, just started becoming an excuse to let 8 year old girls pretend they're teenagers.

LMAO that you're singling out girls. Beyond that though, your post - for all its effort - feels rather ignorant; the "tweenage" target audience has pretty much always been around, what corporate calls it shifts every few decades because marketing to children, more so than any other group, shifts radically with their social interests.

When you're making something for kids, basically everyone knows you have to stratify it more intensely than other age groups because the minds of pre-adolescent (or tween) children vs. a kid in the early and middle stages of childhood are vastly different. Shit like "Nanalan'" made for kids still going through early childhood, might appeal to someone still in the middle stages of child growth; but isn't likely to offer much to a preadolescent who, by then, is going to want something more directly stimulating and engaging to their mind.

And yes, it's largely just a naming scheme to better market to that specific group. What do you think does better in reaching their target audience? A TV block aimed at "preadolescent children" or "Hip Tweens"? And you get it in every age group, not just the tweens. A lot of teenage media is focused on treating the viewers how they want to be treated; with respect, like they're small adults capable of making their own decisions and that their parents are just boring and don't get them. That kind of shit flies way better than "cartoons for adolescents"

The in-between stage of development between childhood and adolescence is literally pre-adolescence, that 9-12 demographic who are at that point in their life where they do tend to be leaving their old toys and games behind and rushing towards more "adult" interests as their personality starts to shape and bodies and minds develop. When you complain that it's just "an excuse to let 8 year old girls pretend they're teenagers"; my dude, that's literally what most preadolescent kids want - to be older and treated like they're older because they're starting to feel like they're not a kid anymore, while simultaneously not quite being there yet. It's why media aimed at them tends to be soft ball versions of more "adult" media - sitcoms and the like.