That's not true, the application, whether you like or not, it full of micro-interactions, well-done animations and transitions, features like the payment or stories, you can take photos directly from the app, etc.

With that many features, it doesn't surprise me that the previous codebase was 1.7M LoC. Sure if you count only the messaging part, I'm fairly certain that the LoC is way lower than this.

It doesn't make sense to compare the number of LoC of messenger to the number of LoC of software like Postgres because Postgres tries to be good at 1 thing and messenger tries to have a ton of features with good UI and UX.

I don't like many of their features (I'm not using the stories or the payment), but some of my friends do and you have to recognize the work that the messenger team did to make them work that well.