> The 16:9 aspect ratio was designed for cinema, not computers
The 4:3 aspect ratio was pretty good for computers displaying a single document or the equivalent; two of those side by side is much better than one when you want side-by-side documents (say, two code windows, or code and related documentstion.) But a single curved monitor is better than one big flat one. In one monitor, that's 8:3, or 24:9. 21:9 isn't perfect for that, but it’s pretty good. 32:9 is equivalentto three side-by-side, which has its uses, too...
Documents are 1:sqrt(2) so side by side would be 2:sqrt(2). For code I find closer to 9:16 to be optimal. Two side by side would be 18:16, also squareish.
You can slice 16:9 into multiple appropriate ratio windows and the limitation becomes pixel density. The ultrawide wastes the extra pixels where you don't see them. Assuming you need at least retina pixel density you won't find it in any reasonably priced ultrawide. It's also just not feasible with current copper cables.
The 4:3 aspect ratio was pretty good for computers displaying a single document or the equivalent; two of those side by side is much better than one when you want side-by-side documents (say, two code windows, or code and related documentstion.) But a single curved monitor is better than one big flat one. In one monitor, that's 8:3, or 24:9. 21:9 isn't perfect for that, but it’s pretty good. 32:9 is equivalentto three side-by-side, which has its uses, too...