If you remove the syntactic sugar like operators (which includes assignment and curly braces - it all desugars into function calls!), R is basically a lazily evaluated Lisp with S-expressions written as C-style function calls. By "lazily evaluated" here I mean that each argument is actually passed as the underlying S-expr + environment in which it was created, so it can either be evaluated when its value is needed, or parsed if the function actually wants to look at the syntax tree instead (which covers a lot of the same ground as macros).
So the existence of R is evidence that Lisp's syntax is a serious problem. If a language providing syntactic sugar has a significantly increased adoption rate, that suggests that the bitter pill of your syntax is a problem :-).
Language adoption is a complicated story. Many Lispers won't agree with me anyway. But I do think the poor uptake of Lisp demands an explanation. Its capabilities are strong, so that's not it. Its lack of syntactic sugar is, to me, the obvious primary cause.
R isn't simply syntactic sugar over a Lisp-like runtime, to make it acceptable, but an implementation of an earlier language S, using Lisp techniques under the hood.
