Another thing younger generations forget is that newer generations rebel against the norm. In America, in particular, there has been going on a rebellion against the individualist Capitalist model from Boomers by Millennials and a call for more co-operative lifestyles. Something traditional D&D parties were built upon.
However, newer generations, are trending to bring selfishness back, a rebellion against the Millennials and Z-generation. Many newer Indie RPGs now feature antagonistic Player-vs-Player rules and hidden agendas in the mechanics. Hidden agendas, especially, are not a co-operative style of play, since why keep a good thing hidden from your team. D&D will lose appeal if it fails to tap into that, yet if it does, it fractures the D&D fandom.