It is less about nerfing than being a different game.
Every game is a challenge, else it would not be a game. It might be called a game by association of the medium used and there is overlap. But I do not consider a kinetic visual novel or a walking simulator to be games. Maybe there are better words to differentiate between the two concepts. You can experience a kinetic novel, but you cannot play it. It has no gameplay, not even decisions. It has no concept of difficulty level or balancing. No competition.
If you make a game accessible by changing the difficulty, you need a new balancing to make the game interesting at that level of difficulty. The worst a game can be, is boring. So if a game is only accessible to someone by playing on the easiest setting, it still needs to provide entertainment. If the entertainment is looking at pretty pictures and listening to a story, ok.
But if gets boring due to this, there is nothing gained by making it accessible. It would be like translating a joke in a different language, where the humor would no longer work. Now it is accessible, but it ain't fun anymore.
Other types of accessibility improvements would only overcome limitations. Like high contrast. You can present the same puzzle to everyone, and elimination of unintended meta difficulty does not change the puzzle. But put an outline around hidden objects in a hidden object game, and it is no hidden object game. You might still make the game "accessible", but it will be a different game.
Same for the non game example of a painting. Sure, you can have a description. But that is a different experience. And it takes a different skill set to create a good description.
Playing a "game" can be about having an experience. But "beating" a game is also a thing.
Regarding your example with the timed mechanism. People have preferences. Those include game mechanics. Like turn based vs. real time. Trying to do both is efficivly twice the work in balancing to give a fun gameplay.
So I am all for the qol features mentioned above that can benefit everyone, so there is a strong argument to have those in the engines for easy usage. But accessibility on the game mechanic design level, maybe even for competitive multiplayer games ... tough. It is nice where possible, but it also hampers creativity if you do lowest common denominator. There is a place for such games, but some people like to play Dark Souls and they also deserve to have games tailored to them.