Offhand, I’d say “too much theoretical math in the starting and middle stages of mastering the language.” Syntax that is based around/descended from APL. Lambda calculus prominently featured in the learning process. Things like that.
It’s definitely a feel argument, and thus highly subjective.
I'm not a FP expert, but I do try to use FP as much as possible and yes, I agree that there is some serious dorkiness possible with certain PLs.
Anecdote, not data, but I've found that Rust, Erlang, and F# (if MS stack) tend to be in the sweet spot of expressive enough without drowning in symbols, without being as mushy as, say, Python/Ruby/pick something.
It’s definitely a feel argument, and thus highly subjective.