This is just plain false. Enough screen brightness works with current generation LCDs. OLED specifically is just incapable of delivering it yet. 500 nits is only bright in a darker room.
Darkening rooms in daytime for non-cinema watching is just a workaround, which is both impractical and not necessarily preferred. 1000-1500 nits is not perceived as bright in daylight, but is perfectly comfortable and legible. A little more would be nice, but not much.
(If you are light sensitive and it hurts because of that, then this is a different topic - but that is not the norm)
Glare from windows or reflected from light walls/furniture can easily exceed that, so any dark scenes (or dark editor theme) are entirely illegible. No amount of screen brightness can make blacks darker under glare, which will show up as the brightest white the screen can produce.
Darkening the environment is the only option for displaying any dark colours and it happens to make high screen brightness unnecessary.
Darkening rooms in daytime for non-cinema watching is just a workaround, which is both impractical and not necessarily preferred. 1000-1500 nits is not perceived as bright in daylight, but is perfectly comfortable and legible. A little more would be nice, but not much.
(If you are light sensitive and it hurts because of that, then this is a different topic - but that is not the norm)