Until about a week prior to TLJ, story-wise, Finn had been so dehumanized by the FO throughout his entire lifetime, he hadn't even given himself a name. In other words, regardless of how old he appears, emotionally speaking, he's probably a severely traumatized adolescent at best. So, he's probably not ready for any kind of romantic relationship. He's basically 7 of 9 a week after her de-Borgification.
... Granted, at no point in either movie has he remotely acted like anyone who's spent a day in a military, so despite Boyega's charismatic performance, his character has been a complete failure from the start. Basically, I won't ever be able to take him seriously until the writers do, nor will I care in the meantime.