The whatzit game was also specifically used for hinting. It was thrown around during Holly's attack to show that Mr Whatsit was behind it. Like Will having Henry behind his neck in season 4. It had a very specific purpose. A piece of foreshadowing like that just randomly being used in the epilogue doesn't make sense, and not in Hopper's cabin.
Plus the Indiana Jones thing in the finale is either backwards foreshadowing (which is stupid and the show has never done, not when it doesn't have any additional implications at all) to the cave plotline, or hinting at Henry's real motivations, or hinting that epilogue Hopper (Indiana Jones in s2) = Henry (Indiana Jones in s5). All scenarios do not make sense in the epilogue. Not if it's never going to be revisited.
For me it's the costumes, maybe because the costumes have always been so heavily detailed and that is true of everything but the ep 7 ESOTSM outfits and the finale. The epilogue costumes are borderline nonsensical if they don't mean everyone's in Camazotz. Like you said about the set designers, it feels like that's what the costume department believes anyway.
I think there's every reason to still believe if you want to. I feel like the main reason I don't is simply that I don't have the energy to, which I'm also highly aware is an illogical and potentially dangerous position to take. Feeling very much like Peter Parker saying, "I can't go to Germany. I got homework." The sheer level of sloppiness that would have to go into the show for all of this to happen is highly unrealistic if I think critically about it but at this point we've been knocked down like 5 times. I still believe the show's worth analysing and I still think pointing out details is fun, but nothing makes any damn sense.