Just moved from my S4 to a S9 45mm. The ambient light sensor is awful when it comes to low-light conditions. The screen gets way too dim. I have brightness turned up to Max and the "always on" feature is disabled. Please give us an option to disable the light sensor.
Apple's product developers don't usually read here in the Support Communities. You can post feedback direct to the product team from the official Feedback page, Feedback - Watch - Apple
You are not the only one seeing it, and I know for a fact it is under review by Apple.
To be fair, I found the display is generally usable after turning up the brightness. Settings > Display & Brightness
The only condition which remained a challenge after adjusting display brightness was bright lighting ahead of me (beyond the watch) and a dark environment behind me so the ambient light sensors saw dark conditions over my shoulder. The combination of reduced display brightness and my eyes adapting to the bright background makes viewing difficult.
I did that as well. I just needed to vent. Hopefully I'm not the only one seeing this. I was tempted to return the S9 just for that glitch alone. However, the battery on my s4 is starting to crap out.
Apple Watch S9 brightness in low light conditions
