I was worried myself about how the U2723QE would look with the M4 Mini but it looks great. I tried it on my parent's 32" 1440p monitor and text didn't look so great to me (quite low PPI and no sub-pixel aliasing doesn't help) but they loved it so I'll probably pick up another Mini for them as MS arbitrarily decided their otherwise perfectly fine PC is obsolete later this year.
Here's one reason why it may be so subjective:
A 27" '4k' UHD display - 163ppi - meets the criteria for "retina" - the pixels appear to be about 1 arc minute* in
angular size - when viewed from a distance of 21". That's pixel size divided by distance & converted from radians to arc minutes - 1 arc minute is equivalent to the definition of "20:20" vision. Not sure Jobs ever described it thus - but that's the basis for "retina".
For an iPhone, you'll maybe view it from half the distance - so you have to double the ppi - hence the over-300ppi resolution for "retina" iPhones.
So, for a 27" UHD display a person with
typical 20:20 eyesight viewing it from a
typical arm's length viewing distance is going to have difficulty seeing 1-pixel-sized artefacts, whether that's seeing jagged edges on curved shapes or artefacts due to fractional scaling.
Trouble is, all of those "typicals" make it all a bit hand-wavy. For starters, your eyesight may vary: 20:20 is not "perfect", and not "poor" but rather (waves hands) "typical" or maybe "not problematic" - then there's a whole bunch of subjective stuff on top of that as to whether you prefer a "crisp" or "softer" display when reading, or how triggered you are by a bit of "shimmer" when scroiling.
Then, you may prefer to sit closer to the screen, or you may buy a larger screen to mount on the wall behind the desk or (if you're, say, a YouTuber doing a comparative review vs. a 5/6k display that you've just been given for free) you might climb on the desk and start taking pictures with your phone and blowing them up 300%...
On top of all that, Apple's silly way of describing "5k downsampled to 4k" as "2560x1440" (It. Just. Isn't) when it actually shows far more detail than any 1440p display just promotes FOMO and resolution anxiety...
The "scaling artefacts" issue is real, but certain widely circulated articles that demonstrate it with extreme-close-up simulations and hyperbolic comments about "horrible" or "unusable" greatly exaggerate the problem... and
nobody seems to consider the fact that you can run a 27" UHD display in 2:1 "1920x1080 (not)" or a 32" UHD in 1:1 "3840x2160" and get a pixel-perfect display. OK, in 2:1 the MacOS UI is a bit large but not "unusable" in any reasonable sense of the word - and most serious apps let you scale your content or font size to taste anyway.
None of that changes the fact that 5k@27" or 6k@32" is still higher resolution than UHD, gives you plenty of headroom
over the "retina" threshold and produces a pixel-perfect display with the "one true MacOS UI size" at 220ppi. Unfortunately
that doesn't change the fact that you can get 3 27" UHD displays for the price of a Studio Display or a 32" UHD display
and a car for the price of the Pro XDR. Even these new, third party options are more expensive than UHD and - so far - unknowns in terms of picture or build quality (except the Samsung which hasn't exactly received rave reviews).
UHD is a perfectly sensible compromise for anybody who doesn't want to splash the cash
or wants to explore alternatives such as multi-display setups, ultrawide or 3:2 screens, OLED, dual purpose TV/monitors...
As for
actual 1440p displays - well, a few years ago they were the bee's knees, and I'm not going to say they are useless. If I had a spare 1440p screen around I'd certainly find a use for it! However, they're not really in contention with 4k displays and
can't display 4k content at all. There may be a niche of users who have
very specific needs that mean 1440p makes sense (maybe refresh rate or colour gamut is more important to you than resolution - there are certainly
specialist 1440p and 1080p displays around) but unless you know why you may be in that group I wouldn't recommend buying less than a 4k UHD display for your Mac.