Functional programming main problem was its mathy roots (too dry, too abstract, too cryptic, too culturally alien). IMO.

Nobody (hyperbole) gives a damn about math, even though they'll all end up using the very same ideas in mainstream clothing.

It might not be obvious to half the dev crowd but most thing they're talking about since 5 years is basically 80s academic FP. Destruct, patterns, lambdas, folds ..