For me, it has to be True Lies which is upscaled badly (4K discs are expensive already) then decide to charge a premium price for that too. The film grain is gone plus a lot of the actor’s faces have been given a “makeover” by turning them into wax figurines. By comparison, The Abyss at least looks better despite that having it’s own issues regarding 4K upscaling.
In regards to 4K remasters via Blu Ray, which one have you seen ends up being a complete waste of money due to bad upscaling from the studio’s end? I would justify the price of 4K discs if the movies in question are upscaled properly whilst retaining the original film grain (and applying HDR correctly), however if it’s a botched job with AI upscaling: it’s a rip off.
I think that the largest issue I’ve seen from higher-resolution video formats isn’t from the remaster as such, but rather that the flaws in the content that worked fine on lower-resolution displays become visible. A special effect or something that blended in wirh the rest of the video suddenly stands out.
For film grain, I’d personally rather not have it, but I use real-time filters that reduce it anyway in video that show a bunch of it, so it being there doesn’t bother me that much unless it’s exceptionally severe. A studio could probably do a better job with offline processing than my computer can in real-time, but…shrugs