Nah i gave up. iPads are cursed.
I got a theory though. I think especially on the 12.9" that the display is too large and in turn it is too flimsy when you tap it. It has too much give maybe.
I can understand where you're coming from given your experiences. That's the important thing. Make decisions based on your own first-hand experiences.
I've owned nearly every generation of iPad from gen 1 to the Mini 5. None of them ever had a dead pixel, or hot pixel. None of them had any noteworthy backlight bleed. The first issue that I ever experienced with an iPad was with the 2015 12.9 iPad Pro.
After 2 years of use, one area of the screen began to intermittently ignore touches. It was the same area where other people were reporting a bright spot developed. That was when I traded it in for a surprisingly good trade-in value at Best Buy... the bright spot issue had been so prevalent (but ignored by Apple itself) that the Best Buy employees were instructed to specifically examine units for the bright spot before accepting the device as a trade-in.
Nearly every model iPad (Pro and non-pro) with a laminated screen larger than 9.7" seems to suffer from this bright spot issue. I'm not saying that every single unit will experience the problem, but that there doesn't seem to be a model where it isn't happening.
What is the root cause for this issue? Only Apple knows. Will Apple address the issue? Since it is hardware-related (not software), they will not proactively deal with it... because if they admit that it is a defect, they will be opening themselves up to millions of units being returned.
If someone owns one of these iPads (laminated screen larger than 9.7") they should determine for themselves if they are willing to live with the possibility of a bright spot developing.
For what it's worth, the only iPads I recommend that people buy (if they're looking for an iPad) is the Mini 5 (which I currently own and absolutely love) and the 8th gen (which I would buy in a heartbeat if I needed something larger than the Mini)... but that's nothing more than my opinion.