(SPOILERS)
Waited to finish the game before reviewing. Final takeaway is that I think the plot's greatest weakness is its constant attempts to pull the rug out from under the player.
There were some interesting themes culminating in the final scenes (unpopular opinion: I liked the ending and would have been mad if it took the indulgent route,) and a handful of moments that were beautiful, evocative, and genuinely heartbreaking.
I think overall, however, these moments were stunted by a plot that was overly reliant on the audience's attachment to the first game, propelled almost exclusively by bad plot devices, and emotionally manipulative/sabotaging to the point of being insulting and often kind of gauche. That last part especially when it comes to many of the flashbacks and achronological scenes in general, though I think a few were successful.
My investment peaked in the last scenes with the insight given into Ellie's grief and the revelation of the hopeful future she lost with Joel, and I think it's genuinely interesting how my feelings kind of unconsciously mirrored Ellie's as I progressed through the plot seeking closure. Unfortunately, I think the deceptive tactics they used to vilify Ellie put a tarnish on the rest of the game, and I would have preferred to see the emotional themes of Ellie's character developed to maturity rather than obscured for the sake of shock/calculated tearjerkers.
Yes, it surprised and upset me with its escalating depictions of violence. Yes, it (again unpopularly) succeeded at making me feel empathy for Abby. And yes, it was definitely a unique experience. But I also think that the much touted anti-violence message lacked the appropriate framing to make it stick, and the more resounding (imo) explorations of grief and guilt were regretfully undeveloped, making Joel's death feel like a waste for much of it.
The senseless violence eclipsed meaningful introspection to such an extent that I prematurely stopped caring about most of the characters, became desensitized to the violence I was supposed to be shamed by, and Ellie's own lack of emotion/self awareness for most of the game left me feeling unconvinced of her motives and alienated from her as a character until the very end. That said, I think the final flashback was very profound and it's been on my mind a lot. I appreciate a lot of what they tried to do with it despite the dubious execution.
TL;DR High highs and very low lows. I think clarity of purpose would have benefited the narrative/player experience far more than a handful of cheap thrills squeezed from shock value. Speaking of cheap, those fake trailers were awful and have damaged my opinion of Naughty Dog forever irrespective of my feelings about the game. :^(