>For me it's hard to believe that 4k on 27" is not enough, I use 1440p 27" 144Hz display as daily driver and barely see any pixels
It's not just about "not seeing any pixels", and "barely see any pixels" is not the same as enjoying hi-res typography and fine detail.
27-inch 1440p monitor is about 108 ppi. That's hardly better from what we used in the 90s and 00s, dpi-wise. Sure, if you haven't used to hi-dpi it looks ok. But try using a 5K/27-inch monitor for a while and then go back to 1440p/27-inch to see the difference you miss.
Now, 4K hi-dpi (pixel doubled) on 27" is 1920x1080.
This makes pixels just fine and detail is great, but everything too large and cuts off screen space, as it's 33% less area than 1440p (which, I presume, you don't use pixel-doubled)
The solution is either 5K/27" (which gives you back the 1440p kind of screen space and UI control size PLUS hi-dpi), or using a non-doubled, fractional resolution, to overcome, (which is not optimal, looks fuzzier, and wastes cpu).
What matters for perception is angular resolution, not DPI. And 27" display covers more visual field that 17" from 90s, so you can and should sit further away from it. Once angle of perceived pixel is smaller than angular resolution of your eye, reducing pixel size only adds to the resolutions of shades you can show to the user in that area (closer to bpp increase, than dpi increase, because you can't see pixels anymore, but still can perceive irregularities of brightness on edges).
It's not just about "not seeing any pixels", and "barely see any pixels" is not the same as enjoying hi-res typography and fine detail.
27-inch 1440p monitor is about 108 ppi. That's hardly better from what we used in the 90s and 00s, dpi-wise. Sure, if you haven't used to hi-dpi it looks ok. But try using a 5K/27-inch monitor for a while and then go back to 1440p/27-inch to see the difference you miss.
Now, 4K hi-dpi (pixel doubled) on 27" is 1920x1080.
This makes pixels just fine and detail is great, but everything too large and cuts off screen space, as it's 33% less area than 1440p (which, I presume, you don't use pixel-doubled)
The solution is either 5K/27" (which gives you back the 1440p kind of screen space and UI control size PLUS hi-dpi), or using a non-doubled, fractional resolution, to overcome, (which is not optimal, looks fuzzier, and wastes cpu).