Here's something that's hard to hear but worth understanding.
Attractiveness in person, the kind that makes someone want to keep talking to you, want to see you again, want to get closer, is not primarily about how your teeth look. It's about your energy. Your presence. The way you make someone feel when they're with you.
But smile insecurity disrupts all of that.
When part of your attention is always managing how you're perceived, monitoring your mouth, calculating when it's safe to laugh, managing the angle of your face, you cannot be fully present. And people feel the absence of presence. They can't name it, but they feel it. You seem slightly guarded. Slightly held back. Maybe a little cold, even when you're warm.