I think Charlie's being grounded from seeing Nick because of bad grades is a good example of this. In a more typical teen drama, this might have become a central plot element. Charlie might have rebelled in a very dramatic or humorous way. Instead, he gets mad at his parents and then quietly subverts the grounding a couple times like a real teenager, but mostly accepts it and carries on the best he can.

Elle and Tao don't directly address what they're going to do about Elle's art school, in another subplot that feels genuine of real teenage experience. Maybe there aren't any good answers. Maybe they really will drift apart. But until events force their actions, they're going to do and be their best.

That's not very dramatic, but it's very real.

Of course, entertainment is often expected to transcend reality. In the case of Heartstopper, grounded reality is, I think, a rare treat for queer youth.