I wrote a long thing about all the things Teens did in previous games but A) moot point, you all know these things and B) regarding the height and being unable to differentiate:
I allow teen pregnancy in my game and there is really no difference between the YA Sims and teens except that the teens can't "Share Big News." Except.... for one mod that has a "I'm too young for this" moodlet that I've seen once after my teen sim was on her third child (turns out she accidentally had the immortal trait so she didn't age and it took FOREVER to understand what was up). I know this lends very little to the discussion except that we shouldn't need mods to make teens be teens.
But pivoting to what COULD be done within the realm of Sims 4...
1) special club activities. We have "play on playground equipment" for kids... there should be activities only teens can do.
2) special lot moodlets. There is a "teen hangout" lot trait-- shouldn't that make a teen feel "hip"?
3) predisposed to social media accounts. It should be way more autonomous for that age group.
4) Prom social events. I mean, come ON.
5) Unique interactions with younger children
6) Unique aspirations.