300ppi is print resolution - yes even for Asian languages. Magazines are printed at that. If I try to focus on the smallest detail on the screen with the smallest type size with my glasses on there is no way I can see pixels. With my glasses off that's a different story. With myopia you can focus on objects as near as 5cm from the eye. I can then see pixels but it's no where near an issue. It is possible you have 20/10 vision which is rare (1%) and that would be the only way a person with normal or corrected vision can possibly see pixels on a 4.7" iPhone.
Yes, 300 ppi is print resolution... yet the iPad Air 2 is 264 ppi. Are you saying the iPad Air 2 is not good enough then? And even worse, the Retina 5K iMac is only 218 ppi. To put it another way, if you're going to use 300 ppi as the gold standard, then Retina iPads, Retina MacBooks, Retina MacBook Pros, and Retina iMacs all fail to meet that standard. Furthermore, the printed page is sized more comparably to an iPad and MacBook than an iPhone.
Oh and 300 dpi is not even the gold standard for print. For high quality photo stuff, people will print at 600 dpi.
The difference here is that some people sometimes hold phones way closer, and part of the reason is that the font sizes are so small on some sites with small phones.
In my case with an iPhone 5S with its tiny font size in Safari on many sites I have a hard time reading it with my glasses on because I have to hold the phone at usual moderate arms' length. The benefit is I see no pixel grid. The downside is I can't read it.
So, if I take my glasses off and hold it closer to read the tiny fonts I can see the pixel grid. However, back in the old days of the 2010 iPhone 4 even with my glasses on I could make out the pixel grid, albeit just barely. Amazing what a difference 6 years makes in terms of close focusing. Imagine if I were 20 years younger.
It also makes a difference how your optometrist corrects your vision. For a myopic patient, some optometrists will occasionally consider very slightly undercorrecting the myopia, to aid reading without reading glasses in mildly presbyopic patients.
As for Asian print, just about nobody prints text at the sizes you often see on phones, unless you're talking about food item ingredients or stuff like that. Books and newspapers, no. Yet Asian kids will read text that small on phones, even if their parents can't.
I'm not saying the pixel density on 3.5", 4", and 4.7" iPhones is terrible. Far from it. It's actually very good, and good enough for most people. However, the pixel density on the 5.5" iPhones is better, and in certain circumstances with a certain segment of the population, it is noticeably so. For that reason, I don't think it's wrong for some people, particularly young people who want to read Asian languages, to prefer a higher pixel density. And it turns out that age demographic represents a large chunk of people who are willing to spend top dollar for their phone addiction.
All that being said, I don't think we can directly compare the claimed pixel densities of current OLED screens to iPhone pixel densities, since they're not a 1:1 comparison.