It's actually wild how terrible Apple Intelligence is. You'd get a better summary by literally copy-pasting the email/text message in any LLaMA model, so I'm not even sure what they're doing to get such awful results.
They just suck at AI. They probably joined the game too late so their in house product is still at the "kinda sucks" phase.
When I tried local llama for this (on a computer), it used tons of battery and memory; I guess it would be hard to use that on mobile device; they probably need to do a lot of work to make it feasible on iOS and locally and it just sucks.
On the positive side, I don't feel bad for having iPhone without Apple Intelligence.