Something's Gotta Give comes off as an argument in praise of older women, which is exactly what one of the characters preaches at the dinner table near the beginning of the film.
If you're writing a script where you are literally trying to prove a premise, you have to hide and sugarcoat it. For example, the writers of Tootsie want to show that men are chauvinists with women, and they do so with a guy forced to dress up as a woman and a swirl of characters creating an intricate plot weave.
When your premise is out in the open like this one is, you cause yourself all kinds of problems. First, your dialogue is stilted. Second, you make the actors look like they are acting whenever they try to say the lines. Third, you kill the plot. If we are waiting for both characters to play out their side of the premise and they do, just as we thought, we have no surprise and no payoff.
Sure enough, tough but brilliant Erica learns to live a little. Harry learns to fall for a woman's "deeper" qualities and decides to spend the rest of his life with a great older woman.
But the writer (and director) gives Erica too little time to fall, based on too little from Harry. It's not as unbelievable as Helen Hunt falling for Nicholson in As Good As It Gets, but it's close.
All love stories are contrived. The trick is to hide the contrivance, give characters some real reasons to fall for each other, and give them enough screen time to do it. Don't underestimate this form. Love is among the most highly choreographed of all genres, and when it's connected with comedy it's even tougher. (See either the Comedy Class or the Love Story Class). But when it is done with a high level of craft, it is always popular.
