Ultracrepidarianism is the habit of giving opinions and advice on matters outside of one’s knowledge.
Cf. “Marxist Glam”
Etymology (Wiki): The term ultracrepidarian was first publicly recorded in 1819 by the essayist William Hazlitt in an open letter to William Gifford, the editor of the Quarterly Review: “You have been well called an Ultra-Crepidarian critic.” It was used again four years later in 1823, in the satire by Hazlitt’s friend Leigh Hunt, Ultra-Crepidarius: a Satire on William Gifford.
(Dictionary.com) 1800-20; ultra– + Latin crepidam ‘sole of a shoe, sandal’ (< Greek krepis ‘shoe’); in allusion to the words of Pliny the Elder ne supra crepidam sutor judicare ‘let the cobbler not judge above the sandal’; cf. the English proverb “let the cobbler stick to his last.”