iPhone screen dims when Playing COD

I have been experiencing this for some time when I play call of duty mobile on my iPhone the screen will start to dim with the iPhone gets hot. The problems I have with this is Apple promoted call of duty in one of the keynotes about the new iPhone. Granted I believe it was regarding the 5G but none the less if the game is made for the iPhone the iPhone should have proper thermal cooling for the parts that are getting hot. Apple promoted gaming on the iPhone all the time. It’s just hard to see the game when the screen dims down so far and I have seen mine go down below 50% because of the heat issue. Once I stop playing after about 2mins the screen brightness randomly brightens. I just think this needs to be addressed at the least looked into thoroughly.

Im using an iPhone 12 Pro