Honestly, I got the impression they were going for a Rom-Com more than anything else. Which is also why Caroline Bingley was wearing what looked like a modern prom dress at one point.

As for Lydia, I got the impression they were trying to skirt around the values dissonance? They specifically say she "ran away." Which is true, but the concern was also that she was shaming their family by taking up with a man prior to being engaged. Which may have been confusing for a modern teen audience, but it also would have been a good look into how people thought back then. However, the film also didn't have the time to go into all of the nuances that would have made it more understandable to a younger audience. So maybe it was both? You're right, though, that the confidential, emotional conversation never happens.