I just found an article about adaptive brightness in Android 12, it seems since the adaptive brightness on android is using machine learning based on daily user behaviour in any lightning condition.
Since I update my zenfone 8 from A11 to A12, the adaptive brightness dim become too low, even though I increase to 80%, and it still not too bright.
What we have to do is reset adaptive brightness manually in the setting, so you can let the device learn your lightning environment habits again after you installed new OS such as from A11 to A12.
Here's how :
Open the Settings app, then go to Apps → See all apps.
Scroll through your app info list and tap on the Device Health Services entry.
Tap the Storage & cache section.
Hit the Manage space button.
Press the Reset adaptive brightness button.
Select OK to save and confirm your choice, and it'll revert to the factory default settings.
It worked for me, and the display become bright again, even though I'm in 65% brightness
