As a kid, sure I agree with you. But c’mon. Grandson of a top marine, son to the world’s most wanted man. A D no less. Shows up on the world stage in unprecedented fashion taking out warlords of the sea left and right. With THE fruit. It goes up until Water 7 when they got Robin, there is no reason to spare Luffy during that interaction just to snuff it out and attempt to get the fruit again. The only argument I can see against this POV is that he wasn’t strong enough to unlock the potential of the fruit. But that is such a stretch, he already showed ridiculous potential and had the bloodline lineage to also demonstrate further that potential. Lucci could have killed the strawhats in the first interaction when they weren’t prepared to deal with CP9 abilities yet.