Reading LoU is really weird to me. The common acronym is TLOU, so that didn't make any sense to me when first reading.
As far as it being immersion breaking. Sure, it is, but it's as immersion breaking as AI is bad in every game.
- In Breath of the WIld enemies follow predictable patterns, and they're locked to an agro range that you can manipulate so that they can't attack you.
- In Horizon enemies have the same agro limit, and for advanced AI and machinary, they have incredibly large blindspots
- In Ghost Recon, again, your companion AI can't be spotted if you're in stealth. It's worse here as all four of your team mates will be in plane site, so there's a much larger opportunity for this to spoil immersion
- In Doom, the enemies are purely reactive, exhibiting very little dynamic or variable behaviour
Naughty Dogs AI is actually some of the better AI in gaming. They move around, flank etc, independently. Communicating with each other and exhibiting relatively complex behaviours, independent of one another, yet at the same time, appearing as if they're working together to take the player character down. The only AI I've really been relatively happy with in these type of video games has been from Uncharted, Killzone, and Fear.
There is no easy way to resolve the issue with Ellie's detection in TLOU, and it's not the result of bad AI. Ellie follows Joel, and therefore, she is a trailing hitbox that can be detected. Making her detectable would require the player continually anticipate her movement. It would make the game, and stealth in particular, several folds more difficult than it currently is.
By not having you worry about her character, you're better able to focus on Joel's role in the game. I don't see how having to continually concern yourself with what the AI is doing would make the game any more immersive. Sure, it has its flaws, but it's the better option.