Haskell is a great example here. Last time I tried to learn it, going on the IRC channel or looking up books it was nothing but a flood of "Oh, don't do that, that's not a good way to do things." It seemed like nothing was really settled and everything was just a little broken.
I mean, Haskell has like what, 2, 3, 4? Major build systems and package repositories? It's a quagmire.
Lisp is also a huge train wreck that way. One does not simply "learn lisp" There's like 20+ different lisp like languages.
The one other thing I'd say is a problem that, especially for typed functional languages, they simply have too many capabilities and features which makes it hard to understand the whole language or how to fit it together. That isn't helped by the fact that some programmers love programming the type system rather than the language itself. Like, cool, my `SuperType` type alias can augment an integer or a record and knows how to add the string `two` to `one` to produce `three` but it's also an impossible to grok program crammed into 800 characters on one line.