Panglossian

adj.
Blindly or naively optimistic.

[After Pangloss, an optimist in Candide, a satire by Voltaire.]

adjective

Expecting a favorable outcome or dwelling on hopeful aspects: optimistic, roseate, rose-colored, rosy, sanguine. Informal upbeat. Idioms: looking on the bright side, looking through rose-colored glasses. See hope/despair.

Ludicrously optimistic. Dr Pangloss is the character in Voltaire's satire Candide who embodies Leibniz's view that this is the best of all possible worlds.

[after Pangloss, the absurd, pedantic tutor of (Voltaire's) Candide < pan, all + Gk glossa, tongue]
often capitalized  blindly or naively optimistic