No, that's not inherently foolish, although it depends a lot on whether one is loving a real person as such through a temporary distance, or if one's projecting an ideal onto someone who's emotionally or physically entirely unreachable. Or is it all simply because of being lonely or just emotional unstable?
For a long-distance relationship one needs to share an established mutual relationship with clear communication, trust, and a realistic plan to eventually close the distance, in essence one needs to love someone who is there as any other normal and sustainable human experience.
One of the dangers is when someone isn't physically or emotionally present, ones brain naturally fills in the gaps, editing out flaws and turning them into an idealized fantasy. One might fall in love with potential or a projection rather than an actual, messy human being.
On the other hand, really pining for someone who's seemingly unattainable can also act as a mere certain situation of safety. It lets one experience the high of romance and longing without the actual real-world vulnerability, compromise, or risk of rejection that comes with any real physical partnership.
Moreover, if the person is emotionally unavailable, or even doesn't reciprocate, one can be staying stuck in a loop that will obviously drain ones energy, let along keep one treating ground no ends. Albeit loving someone from afar even without a guarantee of a shared, everyday reality is indeed not being foolish.
Loving someone in a real, genuine way is in the end always risky, but it reveals also a genuine capacity for warmth, empathy, and devotion to the other. Is love worth the risk? Of course, the downside is that one might be left feeling like something is really wrong with oneself. However, overthinking is also more likely.
It may not be sustainable for the long term. But is it worth the risk, or the experience of sharing that with the person? It could be. You just have to be ready for its share of heartaches too.
