Some of them have both mutable and immutable versions (lists, hashes) where immutability is the default, some are purely functional (Okasaki's data structures implementation https://pkg.racket-lang.org/info/pfds), and some are mutable by default (the "data" package). Most of the stdlib is immutable by default or plain immutable. There is no "slick" syntactic sugar for these by default, but Racket being as good in "language creation" department as it is, there are 3rd party implementations (https://github.com/greghendershott/rackjure).
> the advantage with Clojure is that these things are standard and that everybody else's libraries make use of this stuff
For the most part it is true for Racket, too. Where it differs is syntactic sugar and more complex data structures; I think some of this will change in racket2 (which is being planned if I understand correctly).
> you get a chance to redo the standard library (and tie it into some syntactic sugar) without worrying about compatibility.
That's why every "racket" program starts with a #lang specifier. Racket, in reality, is many different languages at once; because of this design and matching implementation, there is absolutely no problem with redoing stdlib and syntax completely - you can write Racket that is lazy, that is FRP, that is Algol(try it, it's fun!) that is typed or is logic oriented (http://en.wikipedia.org/wiki/Datalog) already. And you can mix modules written in them freely and conveniently (provide in one and require form in the other module are all it takes in practice).
This alone makes Racket so much more flexible than any other language. What Racket lacks now to implement everything Clojure (and other languages) offers as one of the Racket languages are only man-hours of development team. Other, less complicated features from other languages are being ported all the time, for example generator function in a Python style (with yield) implementation is in a stdlib since a long time, so I believe assimilating proven concepts from other languages is both possible and a "Racket way".