34” 3440x1440 is 110 dpi, which is 1x, not retina. To do retina at those sizes you’re looking at 8k. Only dell has an 8k monitor, and it’s not ultrawide, is very expensive, and most of the mac line-up probably can’t drive that many pixels.
Of course, I dont have answers. I didn't say HiDPI displays that suit everyone's needs is available for cheap. However, the main problem is that everyday people have a lot of 1080p 24" monitors sitting around. There were probably fifty to a hundred at my old office. Because we didn't have any huge size requirements or uncommon aspect ratio needs, we were able to take advantage of HiDPI displays that cost to the order of $100. To me that's a price point the average person can afford. If it causes some folks to have to shell out a lot of money to stay on 16:10 or have a reasonably large monitor, that is a reasonable trade off; most users don't need em, hence why it's difficult to find good 16:10 monitors in the first place, for example.
Please point to me a reasonably-priced HiDPI/Retina Ultrawide (at least 34" and 3440x1440 reso) monitor. I couldn't find one.