Several reasons why this doesn't hold up.

I think they had to scramble for a lead because Cyd Charise, who had gotten the part, had to withdraw due to her pregnancy. But if Gigi is true, men in Paris liked them young, moving on to the next one. Even American history has pages of young brides, producing a lot of kids to work the land. That philosophy changed with the evolution of technology and jobs in the city. I hope the recognition of when a mature decision is really made also played a part.

If we can save humanity, we become the caretakers of the world

part of the reason it didn't work for me is because how creepy he was in trying to get her to go out with him. stalking her at her workplace, the entire scene were he sees her is a lesson in how to continually harass a woman when she gives clear signs she's not interested. continues doing so even when she manages to wrestle away from him and return to the table. stalks her at work because she's too polite to reject him and eventfully she has to say yes because ris expected of her and then she falls in love with him. load of crap

Really people? The age difference (19 years) is creepy here, but you have no problem with modern Hollywood casting much older men with much younger women. For example, Harrison Ford paired with Anne Heche (27 year difference). Heck, IRL his own wife Calista (22 years). How about Liam Neeson opposite Olivia Wilde (32 years); Colin Firth (whom I just love) and Emma Stone (28 years); Jack Nicholson and Helen Hunt (26 years)? And those are just ones that come to mind, though I did have to look up the exact differences.

And then there are the hundreds of real life December-May relationships/marriages. Those seem to be okay and never noted as long as the man is the December. But you put Demi Moore with Aston Kucher and all of a sudden she's a cradle snatcher and it's shocking because of the 16 year age difference. The irony in this movie is that Nina Foch is actually 12 years younger than Gene Kelly.

If you think the 19 years here is creepy and disgusting, then surely you feel the same about current casting and real life choices too. Right?

Now, I will agree that what we would consider stalking today, but that was apparently no big deal then, is somewhat disturbing and I don't particularly care for it. OTOH, over the years I've grown to dislike Lise more for stringing him along as she did and him adoring her for it. The justifications are what's forced and somewhat offensive, IMO.

But let's get to the music and dance. There are numerous movie musicals from that time that employ the fantasy dance sequence, so it was kind of de rigueur, especially because audiences expected movie productions to be extravaganzas. As well, there was so much good music and so many talented singers and dancers that it probably seemed a shame to waste them. Fortunately, straight actors weren't usually cast as leads in musicals. When they were, the results were typically as erratic and unsatisfying as today. Marlon Brando in Guys and Dolls comes to mind (shudder). Keep in mind that there weren't 500+ channels and internet and streaming and so forth. Movies, theater, and clubs were common evening entertainment. Movie makers lured in viewers with big, sometimes outrageous theatrical productions.

If you don't like the music, I have no quarrel with you. Individual tastes don't need to be justified or defended. Keep in mind these are some of the styles of music at that time. As a musician, I find much of it hard to beat today. Trained singers and dancers hold far more appeal for me than the "I got up today and decided I wanted to dance or sing" standard prevalent today. The music is boring to you? No problem. I don't like every song in the movie.

It's already hard enough to find somebody special to have a lasting relationship. Don't get hung up over a superficial difference like age. After all, our differences make us stronger and there is beauty in diversity.