To be fair, the amount of text you had to write to explain your ideal solutions (at least to me) hints at the fact that photo management software is very complicated. Specifically, there are lots of use cases and choices to make about the design and implementation, all with their tradeoffs and complexities. Supporting all of them is quite hard to do, so it is no surprise to me this is the state of things right now.
To be fair, the amount of text you had to write to explain your ideal solutions (at least to me) hints at the fact that photo management software is very complicated. Specifically, there are lots of use cases and choices to make about the design and implementation, all with their tradeoffs and complexities. Supporting all of them is quite hard to do, so it is no surprise to me this is the state of things right now.
(disclosure - core Immich maintainer)