It's not by a vast majority of the player base. ( At least not for now)
Here is the definition of
accessibility.
You are confusing usability with accessibility. Even though all of the content is usable by everyone in the game, not all of the content is accessible by them as currently there are not that many effective systems in the game to let people with disabilities such as lack of time, strange working hours social anxiety, ... Experience all the content.
Having said that, as mentioned in my previous posts, I don't think making all of the content accessible by everyone is a good idea, but all of the instances in the world should he accessible at least on one difficulty.
Edit: usable in this context means payable.