I haven’t tracked this down, but I believe the authors of How to Design Programs did some research and basically found that whether FP or OOP is harder depends on which you learned first.
Which kind of makes sense, but then again I learned OOP in college, I always found it really hard to remember all those design patterns they made us learn. Years going on in programming I never really saw any big advantage of OOP hierarchies and spreading one function into 15 different files (yay for the person debugging this).
Then I found out what we call OOP is just a misunderstanding. Erlang kind of did "proper" OOP and that makes sense.
Then I got to functional programming through F# (and Scott Wlaschin's amazing page F# fsharpforfunandprofit.com), and it just immediately clicked. Maybe because Scott's material is so good. But also because there's not so much non-sense boilerplate and extra complexity as you see in every "good" OOP example.
Scott also wrote “Domain Modeling Made Functional”[0], which demonstrates functional modeling of a business system like you’d find in the real world. I found it really helpful even though I don’t work much in F#.
Then I found out what we call OOP is just a misunderstanding. Erlang kind of did "proper" OOP and that makes sense.
Then I got to functional programming through F# (and Scott Wlaschin's amazing page F# fsharpforfunandprofit.com), and it just immediately clicked. Maybe because Scott's material is so good. But also because there's not so much non-sense boilerplate and extra complexity as you see in every "good" OOP example.