Native resolution

"No Apple display ever operates at the full advertised native resolution" is NOT true. By default the MacOS uses retina display mode. Retina display typically uses 2 actual pixels to present a picture to the viewer. This typically means a relatively large sized font but something that looks extremely smooth in the curves and so on. Very similar to anti-aliasing.

Now if you're like me you just want more real estate for your apps, you can just opt to bypass all this. There is a *free* app called "EasyRes" which will let you switch the resolution to exactly what is possible by the monitor and if you want to have 3456 x 2234 on your 16" macbook pro, you can. IF the fonts are too small or begin to look jagged then you'll have to sort that out yourself (e.g. resizing, etc.).

However to say that it "no apple display ever operates ..." ... nah. Not true. It is actually possible, even if it's not common.

For the record, I normally use 2880 x 1800 because after that I find it's a little too narrow sometimes and if I have to increase the font size then it sort of negates the whole purpose because I did it to fit more lines in the screen at once.

Because the font would be so small you could not read it for one. Apple will scale the resolution to keep the sharpness but make it readable.

https://appleinsider.com/inside/macos/tips/what-is-display-scaling-on-mac-and-why-you-probably-shouldnt-worry-about-it

It's not accurate to say that Apple never makes full use of high-PPI displays.

They just don't make use of them for cramming more and more, tinier and tinier, text onto the screen. Commercial book publishing equipment has the resolution to publish all books in 3 point text. Does that mean that you want all of the books in bookstores and libraries to be printed in 3 point text, so as not to "waste" the available resolution?

I'm using a 27" 4K display in Retina "like 2560x1440" mode (one of several available). There are three resolutions involved:

• The "UI looks like" resolution (shown in System Settings > Displays) is 2560x1440.
• The drawing canvas "Resolution:" shown in System Information is 5120x2880 pixels.
• My monitor reports receiving a 4K signal. The system is scaling down from a 5120x2880 pixel level of detail. It is not simply taking a 2560x1440 pixel level of detail and doing the equivalent of "digital zoom".

If you really want to run the highest resolution you need to open the display preferences, then holding the option key select scaled and it should show all the resolutions up to 5K (5120 x 2880) that you can pick as the default. But like I stated before the font will be very small. For me even the default resolution is too small but my eyes are not what they use to be anyway.

Just to add, all Macs operate at their native resolution. For example, even when the resolution is scaled, a 4k video will still display at 4k on a Mac capable of supporting 4k, no matter what the display is scaled to.

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see what resolution you get. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

Did you use the option key when selecting the scaled resolution? It should show 4480 x 2520. See these specs:

iMac 24-inch - Technical Specifications - Apple

If you're running Ventura, Go to System Settings > Displays > Advanced… Enable "Show resolutions as list".

If you have a 24" iMac you should see a resolution of 4480 x 2520 as an option using the option, scaled view to pick from but you might find that too small for everyday use as well..

all monitors I've ever connected to macs have run their native resolution

currently I have a 1080p asus and an old samsung 1280_1024 connected