I don't have any issues with lighting, you seem to be having one or several of the following:
- Light sensitivity - seek a doctor, this is not normal. May be due to stress or neurological disorder, including a minor case of epilepsy.
- Incorrect room light balance - bright lights in a dark room cause issues, do not do this
- Bad monitor calibration - having brightness set to maximum with high contrast - please calibrate your monitor, desktop and game settings
- Incorrect HDR setting, including "fake HDR" and shaders - please exercise proper color calibration
I have never experienced your issues, and neither have anyone i know of. This is definitely some issue on your end. FF14 is, in fact, quite muted and drab compared to many other games.