I used a 43" 4k TV to replace a multi-monitor setup, and the neck and eye strain was brutal for me. Even with a really nice display with a high refresh rate, viewing the corners from that close up was worse than useless. The brightness was difficult to tune down enough to reduce eye strain and from that close up reducing blue light through software wasn't very helpful.

I've since switched to a 32" 4k curved display (still 16:9, not ultrawide) and have been much happier. The curve makes more of the view useful from the periphery and the display has some quality-of-life features, like displaying multiple inputs as separated and ratio-configureable "monitors" in hardware. It's also nice to have controls on the display; the TV relied on the remote, and I kept losing track of it.

The only thing I miss is being able to switch to watching sports at the end of the work day, and being able to cast video to it. Those were luxuries duplicated by other things already in the house. I'd like to say I miss gaming on it but I honestly don't, it's much nicer to not have to extend the keyboard and mouse back far enough to also see the entire display at once.

I work mostly with text and code so the curve isn't an issue, and I could see designers preferring a flat panel to avoid distortion. Otherwise I'm not sure I could go back to having such a large display, much less a 65" display.

EDIT: Per another comment, I have mild hyperopia diagnosed about a year into using this setup, which continued for another year after getting glasses to correct it. My prescription has not changed since getting the new display.