We're talking about displays for gaming here. If you want to watch TV, obviously just use a TV.
I'm not actually sure it is (or its very marginal if so) but I get the point you're trying to make, and here's why its wrong. Say you have a 40" screen which is definitely taller than mine, when gaming on it, you get the exact same vertical content, only bigger (which is entirely relative to your seating distance anyway). However you still get more content at the sides of the screen with the ultrawide. So overall size is irrelevant to vertical content. For gaming, you get more content on screen full stop with ultrawide. Productivity is different since that literally scales with pixel count which would be greater on a 4k screen, but I'd argue the wider aspect ratio is still more beneficial there for reasons outside the scope of this conversation.
Sounds to me like you're now arguing that wider is better so it looks like you're coming round to my argument
You mean like OLED, supercars and enthusiast level GPUs? Since when did niche = not as good?
All modern games support the format so I see no issue in that regard.
No because a lot of games don't allow you to play ultrawide on a 16:9 screen with borders and even where they do, setting it up can be a pita.