Well, I can give some insight. Not sure what happened with 11.5x, but the already s****y atmosphere, haze, washed out colors, got even worse with the 11.51 final release. I see so many streams and screen shots, where there is this blue milky haze at times, so heavily overdone, that it looks like the person intentionally has modified their color and saturation settings. In 11.41, I never had this problem. The colors and vibrancy was muted in typical XP fashion, but was livable. After 11.51, I too have that milky blue/grey washed out haze, anytime fog or haze is in a metar. Honestly, I only updated to 11.51 to keep up with zibo, and the LES SAAB. All my other flying is in MFS2020.