It’s impractical for a game to be equally accessible to everyone, so we can set aside that possibility.
However, designers design for an audience in mind. And that audience can be more or less broad, more or less diverse. That’s a choice that designers make. Let’s set aside cases of physical disability. Let’s talk about action adventure games with strong narratives. If I’m designing one, I might spend a lot of time tuning combat or traversal mechanics to cater to the large part of my audience that is engaged by that stuff. But I might also perceive that basically this same game can provide an enjoyable experience to a different sort of player, one who doesn’t want shooting challenges, etc, but who wants to take part in the adventure’s story. I can accommodate that kind of player–without in any way changing the experience for the first set of players–with an auto-aim function, or by lowering the enemy hit points, or having a game setting that means the player never dies.
As the game designer, I can intend both of these experiences within a single product, and can very simply cater to both. I think what you’ve been saying is that I’ve somehow let the first group of players down. Actually, you’ve said I’m a bad designer who can’t do his job.
The reason I think you’re wrong is that the rationale for having that “no death” button or whatever is a meta-concern. It’s a question of audiences and accessibility. It’s not actually a decision made for the integrity of the gameplay systems, so there is no need for a remedy of that kind.