Why is my screen always so dark?

these past couple weeks or so my phone has been too dark to see when i’m outside.

• it’s NOT low battery
• it’s NOT auto adjusting, i turned both versions of that setting off
• it’s NOT overheating
• it’s NOT set to a low brightness, i have to keep that set to maximum at all times now

I have yet to see a valid answer, and the only thing i can come up with is that my phone (a 13) is suffering from planned obsolescence. the only response i can offer to that is not buying another iPhone.

so can someone please offer me a VALID answer?