OLED phones are bad because of flicker

On iPhones at least you can disable PWM dimming at lower brightness level at the expense of color accuracy. It's in Accessibility/Display settings.

Now tell me a model which has this given that OLEDs are here since iPhone X

Hint: the only one was released in a year that ends with 25

Only if you’re sensitive to that flicker, which most aren’t. Otherwise they’re pretty great.