I think that's where a lot of flames towards Scala from some hard-core FP programmers came from: trying to use Scala as a pure FP language, but having to grapple constantly with the quirks of the underlying OO desugaring.
But I do think your example of typeclasses is a great one. It's a good example of an FP concept (typeclasses thought of as logical constraints to a type variable) desugaring into an OO one (additional implicit arguments).
Regardless, scala3 will make that conversation so much simpler http://dotty.epfl.ch/docs/reference/contextual/type-classes....
True enough that implicitness is not an OO concept in and of itself (I think that was the operative word you're focusing on), but I do think it's the first thing that comes to mind if you're thinking in an OO manner. (Ugh... I keep needing to thread this parameter around... oh I know I could just use this DI library to implicitly insert this parameter for me!)
At my work it's pretty OO, with FP used where convenient. People join and start reading/writing Scala with zero experience or training, and it works out OK.
At Stripe, I understand their Scala is pure FP, with the first onboarding docs discussing "What is a Monad". I assume they need more training for people who don't have a pure-FP background, but if it works for them who am I to judge.
My own personal style is somewhere in between, certainly more FP than at my work, but nowhere near as FP as those who are really into it.