Interesting to see this particular addition. Handy for the players with slower reflexes, utterly useless for speedrunners (unless it messes up with physics somehow)
I also wonder how will achievements be managed while the accessibility turned on. Plenty of people are out there, vocally complaining about "handing out the platinum" to people "that do less effort than I did to earn it".
Some games have separate achievements for separate difficulty levels. I can see how any approach will leave some people annoyed, though. I don't care much about achievements (in 40 years I don't think I've 100% a single game) so I don't really have a dog in the race.
I hope so. As someone who will use the accessibility features, I don't mind separate badges at alll. I don't need the same badge as a speed-runner. I just want to play the game.
I used to be one of those people who thought that it was unfair that they were handing out the achievements for "less effort," 'til somebody pointed out to me that it isn't for less effort. Somebody who needs accommodations would be playing a harder game than somebody who doesn't at default settings. Their difficulty curve is steeper. Accomodations are a way of bringing the difficulty curve more in line with what a non-disabled player would experience.
And besides - most people aren't going to want to completely ruin the game for themselves by sucking out any semblance of difficulty. Most people are still gonna play the game in a way where they get challenged. And even if they do, who cares? That doesn't devalue the work that you did, you know? You still put in that effort yourself, so you can still feel secure in it.
Not coming after you in particular, just talking on a couple of the general points you brought up.