I think a lot of these 'evolutions' tend to be much more one person's creative vision, than a response to the zeitgeist. Although I did notice yesterday in Orc's Nest that the new WoTC 3-book slipcase came with an Anime-style cover...
But current rainbow-coloured D&D seems more about Jeremy Crawford's personal vision, than an attempt to appeal to the largest number of new players. The same for eg 2e Planescape - it was influenced by 1990s Gen-X culture, but was primarily an authorial vision. I think 2014 5e D&D was quite unusual in being designed primarily around market research, and that was only because of the failure of 4e D&D and a resulting lack of confidence in the creative-vision approach.
