Not every game should have difficulty settings. Not every game CAN have difficulty settings.
Moreso, it's not the difficulty of a game that creates accessibility issues; It's the controls, the reaction time required, the nitty gritty game mechanics that create ableism in game design.
Using "all games need an easy mode for accessibility" as a mission statement just complicates the entire problem and doesn't actually further the conversation on accessibility in the games industry.