>>712572512 (OP)
every engine uses a filmic tonemapper now (either ACES or the Uncharted one) which means as colors receive more light, they become more desaturated (more white)
also artists use PBR workflow now where they don't choose colors directly, instead they supply physical properties like roughness which affects the final color. In the old days if you want something blue you paint it blue in the texture, it gets rendered as blue and shown on your monitor as blue. Nowadays artists don't get to choose the exact color.
also everyone slaps volumetric fog on top of the scene to add depth but that also washes everything out
since no-one makes their own engines anymore we are stuck with this look for every game in every genre