I agree with that.
The main difference between Theodore/Samantha vs K/Joi is HER is about
relationships and 2049 is about the
self.
Joi represents K's soul -- what he thinks, what he wants, who he is inside, and why we like him. K is who he is to everyone else; but when he's with Joi he is himself. He knows she's only a program and he reminds us of this when he offers her a cup of coffee or tells her to buckle up; there's always the ironic smile. He knows he's eating bland noodles and that she's nothing but laser beams, but the variety is enough for him. It also allows him the illusion of choice, and the illusion of a life. Her tragedy is his tragedy: discovering that he is Joi.
Discovering he is not special, that he has been following a sort of programming the entire time. First his job, then his "dream," then the resistance, to finally the truth. Now, without Joi, he is faced with having to make a choice. A real one. Not just laser beams.
It is at this point he is born, because here he finally makes his own decision based on the truth.
That's the importance of Joi and her demise and the in-story realization she isn't anything more than her programming. But as
@europe1 mentioned earlier -- at the same time she is more than her programming .... to K, which gets into the Truth vs Meaning. It's the whole replicant metaphor:
does it really matter if you're not real?
What's great about the last act is even though we believe in the goodness of Ryan Gosling, we're not sure what K's intentions are until he commits to them. Even midway into the fight with Luv there's still that inkling K just might kill Deckard.
@Anung Un Rama: I was still saddened by Joi's death because while it's true she is basically a fluffer PS2, the time we spent with her built significance for me.
@moreorless87: Spike Jonze subverts the typical fade-to-black love scene in reframing it as virtual space in which Samantha develops into her own being; it's not really a fade because the black space means something. Their relationship is an exploration of what it means to be in relationship, expectation, attachment, etc. The 2049 scene doesn't have the same purpose, and it surprises me you would want to see more after the marvelous sync-sequence. I'm curious what more you would like to see there. The other function of that scene is to plant the tracking device.
@BisexualMMA: I didn't get too much of an arc to Luv, but I did like how subtly she moved at the beginning. I liked how she bristled when K mentioned with amusement that she was named, and then her furtive flirting.