Accessibility == allowing access to core content / value, and/or removing barriers to this access.
In the product/service context, the core value is usually a clearly defined goal or end result. Whether that goal is achieved is usually a clear yes/no answer, or is at least measurable. Examples:
Accessibility is relatively easy to identify in this context. Different methods of achieving the goal are equivalent, because the important part is the end result, not the means used to achieve it.
For products/services, the ends are the point, not the means.
Artistic works are books, movies, games, poems, plays, etc. Activities are things like board games and sports (physical games) and video games. Note that games can be both artistic works and activities.
In artistic works and activities, the work/activity itself is the core value. The means are the point, not the ends.
Unlike products/services, modifying or enhancing the original is not equivalent to the original - it creates a different work or experience. Cutting a scene from a movie results in a different version of the movie. Riding a bike with training wheels is a different activity than riding a regular bike.
There are very few examples of actual accessibility in artistic works and they are primarily technical/mechanical. Most things commonly considered accessibility in artistic works are instead:
To categorize some specific examples: