There's a major problem with the international web accessibility guideline designed to ensure that web content is as clear and simple as possible.
When text requires reading ability more advanced than the lower secondary education level after removal of proper names and titles, supplemental content, or a version that does not require reading ability more advanced than the lower secondary education level, is available. (Level AAA)
It's a problem of human nature.
Almost everybody who writes web content sincerely believes that what they write is already as clear and simple as possible.
Those who wrote the unreadable criterion above doubtless thought it was as clear and simple as possible.
And yet, according to the very type of readability test recommended in WCAG 2.0, the sentence is extremely difficult to read. A 41-word sentence — when plain language guidelines call for a maximum of 20-odd words!
If readability is so easy to test and the accessibility guideline break its own guideline for readability, what hope is there for the rest of us?