One of the things I find tough to remember to think about once you are an experienced reader of a genre is things that were always problems but that you are used to.
I was reading a book and our delightful female main character ran into a scruffy looking dude right around when she and her long term dude broke up.
Now as an experienced media consumer, you might go, ah yes, that person you trip over right as the clearly not good enough for you person exits the story is your new love interest. Yay for you.
And of course, our character is upset, she misjudges, because it would be weird for her to be like hello hotness while still wiping off tears.
But you the reader know, this is the one, and since you the reader are presumably in a better emotional state, you don't judge new person for their scruffiness, and you forgive main character.
Except a main character who only remembers someone looked scruffy one time, and fails to think about how we all have sweatpants days or whatever, well, if this so-called mistaken identity continues on for too long, even the tropetastic-ness cannot save it, because the main character is now just judgey.
I do sometimes think rom-com patterns exacerbate this. Some rom-coms really traffic in embarrassing the heroine a lot to prove she deserves to have things go her way. And so, through that lens, you can sort of see how you could get to a place where a character stumbling over her next beloved but not seeing him because he's not dressed in a manner she feels a person should be, seems funny.
But the trope doesn't require that. That's just bad execution of the trope.
