it opens auto dimmed to half

I am wallowing in Apple iPhone 12 ****. I pick up my phone and unlock it…dimmed. Put it down for a few seconds on its face…dimmed. I have scoured the internet. I have turned off everything mentioned all the way back to IPhone 7. I have had it. No, it’s not overheating. I have taken it to the iPhone store, only to be told I must be doing something wrong.

is there a good reason not to change phones. Maybe the newest Samsung would be nice.