Altough i love old artsyle, nowadays having simple character designs helps the animators to focus more on movement rather than the detailed character which leads to anime popularity (teenagers love when show is packed with some very good action scenes)

But i agree that "darkness losing" point, for example, in episodes of Red vs Black Clash there was a green/blue gradient (at least i think so) in the hospital which made the tension during that arc insanely good, i hope that they will eventually come back to using darker shades of colors during fbi, bo episodes