and likely I would move back to the country where we both live currently.

First, how would you do that? Work visas are tough to acquire for people outside the EU/Schengen area, even in high demand fields.

My question is, is it naïve to attempt a long distance relationship with someone I will have been dating for three months by the time I leave?

There are tons of factors playing into it (e.g. age, compatibility, timelines, etc.), lots of them you have no control over. I've met my bf while working in his country and we went long distance around 3 months after dating. We only started it because we were already in our later 20s, have both dated extensively before and had compatible timelines and goals. Luckily we're not that far apart and manage to see each other every 5 weeks and are able to spend 3 days up to 5 weeks together each visit. We've travelled together, we've "lived" together for a bit.

So yeah, it's really up to you two what you want to do. If you decide to pursue long distance, you should have a talk about how and when you can potentially close the gap. Try to stay realistic.