By 25x14, do you mean 2560x1440? If so, are you saying that a $15 device will magically make a 2560x1440 monitor higher resolution than 3840x2160? If that's what you're saying, do you have a link that provides some detail on this because I don't believe it.

I'm also unable to believe someone would consider 27" 4K text illegible on a mac since that's what I use that every day and can read text comfortably. Edit: Unless you're using it unscaled, then yeah, text isn't that legible.

These are strange statements to make without any detail.

It isn't a device, it's a software tool. It doesn't make the monitor magically 2x the resolution; it can trick macos to render onto a 5k buffer and then downscale the output to the physical display so it looks not-broken.

https://github.com/waydabber/BetterDisplay

I'm saying macOS is unusable on native resolutions - everything is either too small or too blurry, so a 4k display won't do me any good. 25x14 is the sweet spot for me, but I guess Apple decided I'm holding it wrong, because they want me to get a 5k display to get usable 25x14.