Older guy here (by Reddit standards, 33) in a longer relationship (again, by Reddit standards, 10 years together, married 6).
The OP is right in that from an older person's perspective, most of the relationship advice on Reddit is naive. It's the kind of advice I gave in my late teens/early 20s, which is usually something like "if you're not 100% in love with and 100% attracted to your partner 100% of the time, you should walk".
I won't get into why that's naive and the massive amount of work it takes to keep a sustained relationship going, because it will mostly fall on those same late teen/early 20 something ears, who will use their multitude of life experiences to tell me why I'm wrong. Sry guise, don't care.
Regarding the OP's message and crushes, I would have given the exact same kind of advice when I was at OP's stage (2 years into marriage). At that point your marriage seems so fragile.
Now? Ha ha ha, man, a crush is just a crush. They happen. Even if you and your partner are deeply in love, you can't stop yourself being attracted to other people.
What you can do is stop yourself from acting on it in ways that violate both of your principles regarding your relationship.
My wife and I are both very flirty people, and not just with each other. I've no doubt my wife has flirted with someone she's crushed on. What do I care? It's just flirting. I trust that my wife is an adult with integrity who will choose to keep it at just flirting. Those are our boundaries, which we've discussed ad nauseum, just like OP and his wife.
Half (or more of you) are screaming "omg slippery slope cheater cheater punkin eater omg hormones and lust and stuff". I thought that way, too, when I was younger. I think a lot of that is simply insecurity. At that stage your marriage hasn't built that foundation of faith that your partner won't harm you in some horrible way. You've not yet realized that your marriage is actually pretty resilient assuming you're both working really hard at it.
Every relationship is different. It's up to the two of you to decide what is and is not OK.
Anyway, I'm rambling. Apologies.