When I am speaking on "ultrawide", I am usually referring to the common aspect ratio stated as "21:9".
I argue there is a case for content creation at 21:9 resolutions. Primarily,
- Smartphones are a very common viewing device, and are ever-increasing in lengthier aspect ratios. Many creators already use 18:9 instead of 16:9 for this reason.
- For desktops, folks are very rarely watching in fullscreen mode anyways