I think both Instagram and Discord is quite bad on the UX-front on iOS. Strangely enough Microsoft’s Outlook is quite decent while it still looks a bit distinct. It is not generally true of google’s iOS apps that I assume started using Flutter and it feels from time to time (mostly not-smooth scrolling)
I think Instagram is actually quite fabulous considering how navigating stories has become muscle memory for hundreds of millions of people. And even after they have been around for some time it is still satisfying to tap that profile pic with the ring around it.