You don't need proliferation of features to achieve expressiveness though (see Scheme or lambda calculus).
Most of the cruft in Scala is due to its support of O-O and its attempt to modernize it. Similarly, C++ is a superset of C rather than a complete break from it (and often, in the field, you find people using it as if it were 'C with classes').
Also, the O-O side of Scheme is certainly more powerful than F#'s O-O side; however, overall F# is at least as powerful of a language (and yet it's also much cleaner/internally consistent).
[Also, it takes only one counter-example to disprove 'all those who say that Scala resembles C++ have never worked with either' (which was my original intent here)].