Absolutely irrelevant for what I do with a phone, and I'd wager that 90% of users would not notice the difference.
I don't believe you if that's the case.
If your production volume isn’t high enough to justify a custom screen to be cut you are stuck with what is available on the market.
And even if 5” screens are available now in the form of NOS or upcycled refurbs that may not be the case 2 or 3 not to mention 5+ years down the line.
So you have to go with what not only is available today but with what is still likely to be available throughout the expected usable lifetime of your product.
Display is something I for sure started paying attention to when I was jumping back and forth between Android and Apple when I went from my OnePlus to Apple and then to Samsung noticed differences.
And why should I? Reading text on the web, calling, sms’ing, listening to music or using navigation does not require “next gen” hardware. Hell, it doesn’t even require current gen hardware. It would probably work just fine on 2000s era hardware.