On a scale of 1 to 15, the brightness looks to be cap at around 5. Above 5 the screen flickers but doesn't get any bright. If you go below 5 you start seeing the screen to dim.
Also compared to a Note 10+ and had no issues playing HDR on Netflix and video player correctly. The Note 10+ gets way way brighter in HDR than my S23 which shouldn't be possible specs wise. This could be a region specific or international version problem. Again I repeat this issue isn't exclusive to me but many people are facing it. You should be able to find Samsung Community pages for India region pointing out those issues.
They won't, S21 series owners are having the same issues and has not been fixed yet.
When asking for help, they will either throw some random troubleshooting at you that you have tried a million times already.
They don't care, even when mention that this isn't exclusive to one person but rather an international variant problem. They do not even try diagnosing the issue. If this was a US variant problem it would have been fixed instantly.
All we can do is keep calling out this issue by creating more and more community ages like this and error reporting on Samsung Member app.