I think that Leap’s conflict comes from what she thinks she should be feeling but she is not. And she is trying to find a reason but can’t quite point out why.
“The perfect on paper man”
A job, car, house, can be a set of desirable things, but it is not in itself enough to ignite a relationship. I am sure you have friends who you think are wonderful but you have no romantic interest in. They are all “perfect on paper” but at some point the relationship chose the platonic friendship. It is the same with dating. You may meet the best men, and they may not be meant to be.
After most of my first dates I felt disappointed and was clear that I did not want to keep getting to know the person. If you had a good first date, go for a second and don’t feel you have to make a long term choice after a couple of hours!
“The irresistible fireworks”
Magnetism is indispensable for a ONS/FWB, but many relationships develop and grow organically. Also, is you are sapiosexual or demisexual, you need to connect with the person before feeling sexually attracted. Lust makes you feel alive and sexy, but can also cloud judgement when choosing a partner.
I don’t think not feeling fireworks on the first date means anything. But if there is nothing else than “good on paper”, then definitely it is settling. I once took about 10 dates to figure out if I wanted to pursue a relationship with someone. Don't rush, don't force.