Literally all of that UX is the same and better in other apps though.
For example, every single part of your description applies to video and text conversations with my SO and friends, except we all use Signal. It "just works", and better than Facetime because it doesn't matter what device my SO and friends have.
With Facetime it doesn't "just work" at all with the large number of people I know who don't have Apple. That's a huge disadvantage which means that Facetime UX sucks.