Panglossian

Etymology

From Dr. Pangloss, the tutor in Voltaire’s 1759 satire "Candide," who keeps insisting that "all is for the best in this best of all possible worlds" even as he and his pupil endure war, disease, and disaster. Voltaire was mocking the philosopher Leibniz’s optimism. The adjective names that determined, reality-proof cheerfulness.

adjective · /pan-GLOS-ee-un/
Naively or blindly optimistic, insisting all is well despite clear evidence to the contrary.
What it names
Optimism that has hardened into denial — use it for the cheerful conviction that everything is fine even as the situation visibly falls apart.
Example
His panglossian assurance that the market would "sort itself out" looked reckless once the third client walked away.
Related idea
Optimistic is a neutral or positive trait; panglossian is pointedly critical, implying the optimism is delusional and ignores plain warning signs.