Many readers of science fiction have a theory of “accessibility” that is absolute, static, essentialist, substantive, and nevertheless unduly personal. Let’s call it T1.
T1: is accessible (by implication: in general) that which I found accessible at the moment I read it.
My own theory of accessibility is relativist, historical, contingent, tautological, and impersonal.
T2: is “accessible” that which is accessible to someone in a context that is changing, multiple, singular, and non-universalisable.
Thus, accessibility-1 ≠ accessibility-2
For example, I read DUNE at a relatively young age (14), and I found it immediately accessible. Today Denis Villeneuve is obliged to create a dumbed-down DUNE, without inner dialogue (i.e. not DUNE at all) to make it “accessible” (for the public to delude itself that it has access).
I deal with the example of DUNE from the point of view of the relativity of accessibility in greater detail here: