Feelings I had for my classmate were obviously one-sided (pretty sure of it), so I made a reasonable decision to never confess to not make things awkward. In a few years since we graduated I finally moved on, although I never loved anyone this much since.
Yet all this time I had a desire to tell her about them. I would definitely want to know if someone loved me this much ever. Would she? I don’t know. I don’t even know if she is in a relationship right now or not.
I would really want to cite some scientific study that “Over 80% of girls have their self-confidence lifted after being told they were secretly admired (p<0.05)”, but can’t find one.
Additionally, even if there is no reciprocation expected, from their perspective, they will think this is in the hopes of reciprocation. And the more OP tries to convince them it’s not, the less convincing it will be. That kind of contact, regarding feelings from the past, just makes one instantly defensive and apprehensive about the idea that they may soon have to rebuff an advance. Which means finding any excuse to not socialize, respond to texts only minimally, don’t do anything which could feed into the idea that you are getting closer to them which could provoke an advance with underlying expectations and potentially a negative reaction upon rejection. It’s an inherently uncomfortable situation because of that underlying subtext of motive that doesn’t go away with any amount of explanation. There are many routes into so many open hearts out in the world. But this route does not lead to love, platonic or otherwise.