The issue surrounding the downgrade outrage/discourse is that it assumes that companies are going out of their way to mislead people. If they were really trying to do that in earnest, they'd continue showing footage that doesn't represent the game right up until the game hits shelves. That simply isn't the case.
The major problem you have is that vertical slices, which the majority of these demos are, are purpose built and often early in development when optimisations haven't been finalised. I have no doubt, for example, that the footage of GoT and The Last of Us Part II were running on PS4 Pro and that's what those teams were shooting for. However that was two years ago, when the games likely weren't even feature complete.
There are so many hurdles that can arise in 6 months, let alone two years of game development that can lead to instances where art direction changes, lighting has to be scaled back etc. It's just the reality of making videogames. This would be less of an issue if games weren't announced as early as they are, but then not announcing games has it's implications as well.
No, it's not a 'real problem' in the industry. This logic would hold up if subsequent trailers for the two games referenced in this thread didn't have plenty of media shown in the run up to launch which captured millions of views. And it's not like people are watching a trailer from two years ago, not seeing anything about the game until launch and buying blind based on the trailer they saw two years ago. People don't do that, not on any meaningful scale.