I'm not sure if it matters whether one says it "first" or not or why the order matters. You say it when you mean it and you say it when you want to say it. If the woman or the man says it first, I'm not sure what that implies or means. I don't put any importance on saying it first, just saying it so it means something. Why do you think it matters who says it first?
And one person didn't ruin it, it was a few episodes with people who I thought I had a real connection with that ruined it. It took the "oh well" episode and then my ex-wife saying it constantly while obviously not living it to do that. Over time, not only through my own experiences but hearing about the experiences of others (which I didn't go into), I realized that people said it without taking it seriously. Again, to use the religious example, I've known too many people who say "I'm a Christian" and think that only means going to church and not living their faith, which was only one of the many reasons why I ended up not following that, or really any, religion, including atheism (which to me is just another religion). I've also heard too many people say "I love you" and clearly not mean it, or say it for some other reason than to commit themselves to some purpose with another person. I don't want to be like that, so I'm doing my best not to be. It's not spoiled for me forever, either, but it is severely maimed.