It's precisely this, as the screenshot comparisons have demonstrated. The "remaster" terminology is strictly a marketing thing. I'm viewing this more as a $10 DLC containing a res bump, DualSense functionality, a new mode, some extra levels, and a few other bells and whistles.
I won't go too deep into responding to... all of this, as it's mostly of the same drum that's been beaten for years now. Agree to disagree type deal. I view this thread as more about a remaster, as opposed to a springboard for a wider reaching discussion about the merit (or lack thereof) of video game storytelling and cinematic games. I'll just say I think it's a dodgy, kinda condescending take that people are "missing the point" when they play a game for story, as people have, and will continue to play games for a variety of different reasons. On a personal level, I can appreciate pure gameplay games like Hotline Miami or Cuphead just the same as a more cinematic offering like TLoU2, or games with an even greater emphasis on narrative, like Life is Strange or SOMA. There's gamey games, cinematic games, games in which you do nothing but read dialogue boxes, and so on.
(On top of that, TLoU2 is often considered one of the best third-person shooters in recent years, so I'm not seeing a mechanical deficiency in the gameplay.)