Have you double-checked various display settings (including those under accessibility) to make sure that something isn't turned on that might be affecting this? Have you also tried recalibrating auto-brightness (assuming you have it enabled)?
Ah, thank you. Auto-brightness was reenabled after the update.
[doublepost=1528517961][/doublepost]It was the “reduce whitepoint” setting. It was more aggressive in 11. I can’t believe how bright the screen is with this off. I wish I knew all along.