You touch on so many important and related concepts in this excellent piece: a distrust of expertise, the Dunning-Kruger effect, relativity over truth, disinformation. It makes sense that we need a whole discipline to study these!

For what it's worth, there is no Greek word agnosis (ἄγνωσις), though it's a perfectly sensible formation. But it would be a noun, not an adjective. Agnotology is probably formed from agnotos (ἄγνωτος), a variation of agnostos (ἄγνωστος), adjectives which mean "not knowing" or "unknown."