Room is way too bright.

@OP - curtains on your windows and acoustic treatment correctly applied to the available surfaces.

The point of first reflection is where the off axis sound from the loudspeaker meets the wall and reflects off it. That is where you apply treatment to the sidewalls.

The aim of acoustic treatment is to stop reflected sound reaching the listener's ears out of phase and confusing imaging etc. It can make the sound appear bright due to the excess of reflected energy.

Dense drapes.  Ask your sig o. to choose color. (This is not hard.)

Thanks to all for your many suggestions and comments. 
And yes, I should have done a bit more research before asking about reflection points. My apologies. 

Finding the First Point of Reflection 
 

https://youtu.be/fs_0hnD_JNQ?si=dS8IqX8E2zCYmh00

I have 17 windows in my large listening room. Using Marigo tuning dots made huge positive difference with no downside. Visually my wife initially did not like but got used to the look after a week or so.

https://marigoaudio.com/zw-window-resonance-damping-discs/