I think it would do good to modern teenagers to be re-introduced to the idea of unrequited love. Like yes, you're wildly in love with this person who doesn't like you, or if you already bungled it, might actually be actively repulsed by you since you unintentionally creeped them out. And it's painful and tragic and it hurts. That happens sometimes. So what can you do? Honestly nothing, other than to mope about it and suffer through it like it's a long, hard bout of illness that takes months or even years to recover from.
And I think kids should be taught that this isn't just fine and normal, but that you totally can - and actually should - romanticise it. Because since there's nothing else you can do about that sort of thing, you might as well have fun having it. You do get to be the the Tragic Suffering Protagonist about it. It's a beautiful, keen and unique sort of pain that is your own personal tragedy and 100% a you problem.
The idea that the only acceptable outcome of falling in love with someone is a relationship with the object of that desire is genuinely dangerous. The idea that the only way to a happily ever after is to "win them over", get out of the friend zone, finally do some feat that'll impress them or prove your worth and finally get the girl. That's not how it works, that's not how any of this works.
Moping isn't inherently bad for you. Okay of course it's possible to spend too much time wallowing in self-pity, but it's good for you to indulge in it as needed. The difference between poison and medicine is dosage, and everyone is allowed to have a little bit of small personal tragedy sometimes, as a treat. You have to do it sometimes just to get it out of your system, be sad about something for long enough to simply get bored of that, and go do something else.
And not to get "A spoonful of sugar makes the medicine go down" stuck in your head, but sometimes that's the key to it. If the only way to go through something is to suffer through it, might as well make it sweet. Sometimes you just gotta be like "I love her and her happiness means more to me than my own, and she does not want me, so therefore I must do this Noble Sacrifice and suffer in silence and simply let her be happy without me" for like six months or a year until you're done being like that and over with it.
I don't know who the fuck thought it was a good idea to instead teach kids that the only acceptable thing to do is to keep bothering the person you like until they give in in and let you out of the ~friend zone~ and you win. That's just not healthy or helpful for anyone involved.